Catholic Tradition has always stressed a fundamental connection between holiness of life (or at least a sincere striving after holiness) and theological insight. The greatest theologians of the Church were also the greatest saints. This personal holiness is, I think, responsible for the amazing clarity and relevance of much of the writings of the saints. The writings of Augustine, Aquinas, Bernard, Gregory the Great, Ignatius Loyola and Newman, besides being treasuries of wisdom, also possess a certain style and clarity that recommends them to the reader. I have noticed that many theologians of greater learning but less sanctity cannot write so well as the saints; the writings of the saints never have that drab, academic feel that sometimes comes when reading the writings of those who were advanced in learning but nowhere near as eminently holy.
In my opinion, this clarity of expression comes not from any stylistic considerations but from the degree of insight with which the saints peer into the mysteries of the faith. In other words, the intelligence and clarity of the saints in speaking and writing about the content of Revelation is directly related to their fidelity to the life of grace. Holiness of life envelops the saint, knowingly or unknowingly, in the sensus fidelium, which enables them to intuitely understand the Faith unerringly and see the truth simply and clearly; recall the marvelously simple but profound answers given by St. Joan of Arc at her trial. In Catholicism, there is a very vital link between personal holiness and theological insight.
However, it is the former which gives rise to the latter, not vice-versa. As we know from many examples, not least of which those spoken by our Lord with reference to the Pharisees, one can know Scripture and understand theology and still be a jerk. Yet we might also reply that those who learn Scripture and theology in a Pharisaical manner have not really learned it. They have perhaps wrapped their mind around a shell of it, but somehow managed to miss the essence of the Gospel entirely. He who truly knows theology knows that theological truths are transformative, as Pope Benedict pointed out in Spes Salvi. He who learns theology but fails to let the Holy Spirit transform him has not really understood what it is he is studying - he who knows theology but hardens his heart against the truths of theology does not really know theology. Thus, in Catholicism at least, there is no real tension between the theologian and the saint. The saint is the most insightful theologian and the theologian who takes his theology seriously will become saintly.
Those who have been around Protestants for any amount of time, especially evangelicals, know that this tension between theological learning and personal piety does in fact exist in Protestantism. Traditional Protestantism has always harbored a suspicious of too much theological learning, viewing an erudite and systematic theology as somehow detrimental to the life of faith. Anyone who has spoken at length with evangelical Protestants, or those of the Pentecostal persuasion, have no doubt heard of the dichotomy between real, saving faith and mere "religion", which is associated with institutional churches and theological study. It is somewhat axiomatic in many forms of Protestantism that too much theological study leads to the believer getting lost amidst a web of "cold Christs and tangled Trinities", all the while missing the simple, saving faith that is alone capable of imparting salvation. Many times, when speaking with Protestants, if the discussion gets to theological, they will back away and say something like, "Yeah, but what is really important is that I have Jesus in my heart. It doesn't matter how sophisticated your theology is if you don't have Jesus in your heart."
Why does Protestantism seem to harbor an inherent distrust towards too much theological learning? I think it has to do with the origin of Protestantism itself, in a twofold sense: first, because of Protestantism's birth in the context of a revolt against Catholic theology in general and Scholastic theology in particular - recall Luther's bombastic assaults against Scholastic theology and patristics at the Diet of Worms when debating Johann Eck and later St. Cajetan - and secondly, the adoption by most Protestants of a soteriology based on the dogma of sola fide.
The first point is well established: Protestant theology was fueled by a rejection of Thomist theology and, in a broader sense, a reaction against the application of reason to theology. The second point, regarding sola fide, needs a bit more fleshing out. For Luther and the early Protestants, salvation is procured according to the doctrine of sola fide, by which a person is justified by nothing other than faith alone in the saving work of Jesus Christ. This act of faith is exemplified by a very radical and individual commitment to Jesus Christ, which is very often a matter more emotional than intellectual. Later evangelical Protestantism stressed the fundamental emotional nature of the Christian's act of faith, which necessarily put it at odds with any perceived intellectualism. Reason, theology, intellectualism - these are things that stand in the way of faith rather than aid it. True conversion will always be discernible by the believer's emotional dedication to God, sometimes in spite of any theological knowledge. In this sort of Protestantism, it is theology that is a handmaid to the emotions. This, I think, is a result of Protestantism placing the crux of its soteriology on the believer's sola fide act of faith in Christ without any reference to anything else (sacraments, Church, doctrine, discipline, etc).
The interesting question is if such a schism between piety and theology is developing in Catholicism as well. It has happened before, in the form of 17th century Pietism. Yet I think it might be returning now in a different, less elitist form. Beginning in the aftermath of Vatican II, many Catholic leaders advocated a "Protestantizing" of the Catholic Mass, in the hopes that fostering a little more emotionalism would make the Mass more "relevant" to the faithful. This, I believe, is a subtle form of Modernism, due to its emphasis on the subjective experience of the believer as paramount in their spiritual life. It is undeniable that there exists today a very large subgroup within the Church that values the believer's emotional state much more than doctrinal or disciplinary considerations, essentially severing the relationship between orthodoxy and orthopraxy. I'm not going to engage in the fruitless task of trying to point out who is doing this, exactly, but I'm thinking, for example, of those who encourage anybody and everybody to go up to Communion all the time, even if in a state of unconfessed mortal sin. One time, as I was refraining from going up to Communion, a certain woman came up to me and encouraged me to go forward anyway. I said I had not been to Confession and had committed a serious sin; she said, "Oh, that doesn't matter. Jesus would want you to come to Him." This is exactly the sort of thing I am talking about - doctrine and theology is thrown out as obstacles to loving God.
Of course, one who takes such an approach of discarding theology for the sake of loving God will neither love God nor understand any theology. I do fear, however, that many lay Catholics, and even many bishops, have begun to take this approach to the Faith. When we often say that our faith is being "Protestantized", too often we are making references to only the extrinsic elements of our faith - music, decorum, etc. The true Protestantization of Catholicism is something happening in our hearts, in what we consider important and how we approach the deposit of faith. Is it a regula fidei that keeps our feet firmly on the narrow path leading to salvation, the faith which, as it says in the Athanasiuan Creed, "except every one do keep whole and undefiled; without doubt he shall perish everlastingly"? Or, do we find in the Church's doctrines something that we feel restrains us and interferes with our worship of God? This is where we need to look when examining the question of the Protestantization of our Faith. Like everything else, it starts with our fundamental philosophy about the nature of revealed Truth.