after all, Aristotle and Plato were alive at the same time, so pre-Aristotelian also doesn't work in that regard

That's fair. I don't really think "pre-Aristotelian" is a particularly good categorization of philosophers though, just a funny rejection of the term "pre-Socratics".

Really the big gap between Plato and the pre-Socratics is that we have many intact texts by Plato, while with the pre-Socratics we have only a handful of quotations preserved in later texts and some dubious paraphrase and summaries, so it's hard to pin down exactly what was going on. But, as far as I can tell, it was really Parmenides and his followers (like Zeno) who established the need for a more rigorous approach. For example: great developments in logic were needed to defeat their arguments that motion and plurality were impossible and only an illusion.

Platonists might not have caused the cooption of Christianity, but most of the really objectionable elements of Christianity are Platonic. Like I'm 100% not a Christian of any kind, but Jesus seemed like kind of a cool dude who wanted to create the kingdom of heaven on earth: a just society were people hold all things in common and shit. All the metaphysical bullshit about souls and the trinity and hating your body and shit is from Plato, Pythagoras, Orphism, and shit like that.