The fandom wiki. Whenever I need lore trivia, I go there.
The timeline there contradicts you.
Firstly, Khas’ khala didn’t end the aeon overnight. It took him an unspecified length of time to reunite the protoss. The zerg ate the xel’naga and left sometime during or prior to this period. No date is ever given for these events. Even with the nonsense retcons, the only date we have is the sparking of the psionic matrix, which was circa 500 BC.
Secondly, other time statements given contradict this. The Overmind conquered and left Zerus within a few centuries according to the game manual. In Episode 2 the Overmind states that it (and by extension the zerg swarm) lived for “countless millennia.”
Thirdly, this is a retcon and it doesn’t even make sense by its own logic. Khas rediscovered the khala (i.e. the empathy network/power source/afterlife/whatever, not the religion), he didn’t create it. The aeon started after the protoss withdrew from the khala. The xel’naga should logically have awoken while Amon was still on Aiur, or by the Aeon if the “absence” they felt was the absence of the khala. For that matter, why wouldn’t they sense the Overmind? It’s basically a sapient khala itself, powered by their void!
(BTW it makes no sense that the presence of the khala would be an absence, because that’s an oxymoron. What, did the khala drain power from the void? That just raises more questions!)
The wiki states that the aeon was the bloodiest war in galactic history, encompassed many planets, and lasted many millennia.
Your information is outdated. I don’t know what else to tell you.