There is no secret platonic influence in catholicism. In the latin church, it's openly encouraged. I was just discussing platonic ideals after mass today with fellow parishioners and how important it is to pursue truth. The priest had even mentioned Plato in his homily on the nature of truth
There's nothing secret here. Christianity is openly and unashamedly compatible with many aspects of Plato's philosophy. In fact, the catholic church has also ruled on the validity of other similarly secular philosophies of other civilizations (see the Chinese rites controversy or Merton's books on Taoism --
Christ the eternal Tao). In general, other than the protestants, Christianity does not require you to immediately reject the works of secular philosophers.
In fact, Islam and christianity are why we still study Plato today. There is no secret or conspiracy.