My understanding, which was never great and is imperfectly recalled:

Augustine was the foundation of Neoplatonism in the Medieval church, which was it's guiding philosophy (to some great extent) for centuries.

The works of Aristotle were lost to them. They knew of Aristotle but didn't have his writings. Around the time of Thomas Aquinas, Aristotle's works were rediscovered, having been preserved in the Muslim world. Aquinas' great task was reconciling them with the existing church.