Questions & Mysteries Why did the Twenty Kingdoms overthrow the GK in the first place?

By now, we now the gist; there was an ancient Great Kingdom that prospered during the Void Century, 20 Kingdoms made an alliance to overthrow them, virtually nothing left of said kingdom, the alliance formed the World Government, yadda yadda yadda.

But it's never been touched on about *why* the Alliance was formed in the first place, or why they so throughly eliminated the Great Kingdom, down to banning any history about that century. If it was a morally grey, ambiguous situation, then logically, the WG would have spinned propaganda about it to make it seem like they were the good guys, but nope, they totally just covered everything up. So, something about this war had to be hidden for a reason, like say....they were the aggressors and did some nasty shit to win, right?

Also, we know the Great Kingdom had ties to the Fishmen, the Sky Peoples, the Minkmen (through Wano), and possibly was the Lunarian Kingdom who lived on the Red Line. I guess the Giants too, via the Jaguar Clan. Was all this just caused by envy and hatred of the Humanocentrist Kingdoms being overshadowed by a non-human, racially friendly society?

And where does Imu come into all this? Why did the twenty kingdoms secretly make him their king?
1. Likely jealousy and fear. The ancient kingdom had technology millennia ahead of all the other kingdoms. Including a superweapon such as pluton.

2. Imu was probably the strongest warrior on the side of the world government who was gifted immortality and as such demanded to be made king and no one could argue it.

Warchief Sanji D Goat

Future of the Marines!⚓
I also remembered something. The ancestor to the Donquixote Family also enslaved the Tontatta, too. Maybe it really was just as petty as them being racist assholes.
Sounds like Murica back in the 1900s.
Problem with that resides in the alliance with alabasta. The Nefertari never showed any issue with non humans and we know they were at least allied against the ancient kingdom
Maybe the ruler of Alabasta was someone else?

Queen Lily wasn't really considered a "King" unless Queen is considered "King" according to Imu.
This is just my theory: Imu was from the Kingdom, but was a misfit and outcast (Maybe a bastard child of the King?), and his hatred eventually worsened to the point where he'd rather trick the stupid humans below to destroy his own people and rule over them as the last of the "Gods".

He came to the Kings, told them lies and half-truths, stoking their own ambitions, and after they won, he was deified, and officially vanishes from rule from the shadows as King of the World. And became immortal, somehow.