It's a good question, but the answer stares us in the face from history. Christianity has been a hybrid religion from its inception, as it combined Judaism with Greek and Roman sources. So Christian leaders had to wrestle with the intellectual side of paganism even as the old world fell away. Augustine wrestled, for example, with Neoplatonism.

But this understates the matter since it wasn't really a question of "wrestling." Christians weren't tolerant of opposing worldviews, the way polytheistic pagans were, so Christendom had to stand supreme. Christian leaders had to show there was no justification whatsoever for rejecting their worldview because heaven and hell were on the line. Thus, they had to incorporate reason and philosophy into their religion to show there was no excuse, and to justify the totalitarian dimensions of Christian imperialism.