In the Early Church, the pagan world was very Hellenistic - and most of the intellectuals of that time were taught the teachings of Plato. Thus, the Early Church made extensive use of Platonism to dialogue with the pagans on their own terms. In many areas, they Christianized the philosophy. Later on in the Christian West, Aristotle was rediscovered and the majority of the Faith was re-articulated in that school of thought, though Platonic thought never left.
As for being required - no, it isn't. A philosophical school is like a spoken language - every one can communicate the basic points - and some are better at certain details than others.