Priests on the Nile used a lunar calendar to predict the phases of the Nile instead of the Egyptian solar calendar used for civil projects.
If Solon misunderstood 9000 lunar calendar periods for 9000 solar calendar periods and Plato had Critias quote that same figure then the math says:
9000 lunar calendar periods/12 months per year = 750 years
Critias was born in 460b.
460bc - 750 years = 1210bc
1206bc is the generally-accepted date of the bronze age collapse in the Mediterranean after which the Sea Peoples descended upon the southeastern Mediterranean and Egypt. These invaders included the Peleset who are believed to be the Phoenicians/Philistines whom the Bible claims came from Caphtor (i.e. Crete).
Plato's 1210bc is curiously close to this known historic date of 1206bc. Possibly the Peleset introduced the Egyptians to the story of the destruction of their ancestral home at this time and the Egyptians associated this tale of destruction with the date that the story came to them instead of the original 1628bc date of the destruction of Santorini/Crete.
As a precedent, an existing new kingdom temple mentions the destruction of Caphra (Crete) and curiously called "an island in the west" that was destroyed because its people became wicked.
The people of Troy were genetically-related to the people of Crete and Santorini, and possibly culturally related. Perhaps Troy even received some of their emigrants. We know that the Greeks fought the Trojans as alluded to in the tale of Atlantis.
The other "details" of Plato's story of Atlantis are mostly the craft of story telling.
This explanation seems plausible to me.