Old Gods are stronger than Dimensius anyways so the Void Lords pretty much used up their power to gain a foothold into the Great Dark Beyond then started eating each other until Dimensius was the last one then got killed by Xal’atath.
Of course the Nathrezim weren’t going to tell Sargeras that so they lied and used the dead Void Lords as scapegoats knowing they can’t defend themselves.
Xal’atath ruled the Void until the Old Gods took over after Sargeras had a run in with them banishing them to the Void.
Then she took refuge on Azeroth and trying to claim power from N’Zoth only to lose and be captured.