Prior to the Scientific Revolution, being a "scientist" required surprisingly little rigor and little to no skepticism. "Scientists" like Aristotle, Pliny the Elder, Avicenna, and Nicholas of Cusa were really just people with varied interests, not that different from old men these days who are into fishing but also into woodworking, playing the fiddle, and fixing their own cars. In fact, up until the Enlightenment era, practically nobody ever considered the possibility that science and a belief in God might be incompatible. People who did "science" simply collected bits and pieces of knowledge on, say, the stars, the rocks, or the internal organs of animals. The ultimate truth of the world, and of the universe, was believed to reside in God and the study of God (theology), not in anything related to the study of shells and stars.

Also, back in the Middle Ages, the Pope was a highly political figure, not just a ceremonial figure that was relegated to the position of saying nice things inspired by the Bible. Being the Pope implied possessing a great degree of pragmatic thinking and an ability to make deals, for Popes had to deal with various groups inside the Church just as he had to deal with kings, generals, and even high-ranking authorities from other religions. A Pope could not afford to be a shut-in mystic monk who would be self-absorbed in his own delusions.

Mysticism is not compatible with being rational, but rationality is very much compatible with pragmatism, and religious people can be either mystic or pragmatic, not necessarily only one or the other.