You know, the Sea Peoples attacked Egypt under Rameses III around 1200 BC. Let's all acknowledge that this date is over eight thousand years after Atlantis supposedly sank.
Regarding Crantor - you have a real problem since his works are lost. Proclus never actually states, however, that Crantor claimed to have seen these pillars:
say, that it is a mere history, which was the opinion of Crantor, the first
interpreter of Plato, who says, that Plato was derided by those of his
time, as not being the inventor of the
Republic, but transcribing what the
Egyptians had written on this subject; and that he so far regards
what is said by these deriders as to refer to the Egyptians this history
about the Athenians and Atlantics, and to believe that the Athenians
once lived conformably to this polity. Crantor adds, that this is testified
by the prophets of the Egyptians, who assert that these particulars
[which are narrated by Plato] are written on pillars which are still
From Proclus:Commentary on the Timaeus of Plato
I don't see Proclus claiming Crantor as a "witness" to anything there. The above statements by Proclus, which he (somewhat) attributes to Crantor, are merely a restatement of what Plato himself stated in Timaeus, IMO.