Either way, i'm completely lost as to why they would change the cast in the first place.
Probably for the same reason that Nintendo relieved 4Kids of their Pokemon anime dubbing duty.
As a rule, you, as a company, stand to save money and have more say in how things work, when you predominantly work with talent that either a) doesn't belong to unions like 4Kids/Ocean, or b) is willing to work outside contract deals pertaining to said dubbing groups. This is the same thing that Capcom has done for years on end, for multiple projects. For example, Sam Riegel/Regal (Donatello on the 2K3 TMNT toon, among others!) has done work for plenty of different works of animation and video games, but is a non-union worker. That makes him more attractive to parties like Capcom, because it doesn't mean that you have to deal with the union.
As the story goes, Sega originally only wanted Pollock to replace Deem Bristow as Eggman. But 4Kids, as the ones who represented Bristow at the time, had more say in the matter. Now that it seems like Bristow doesn't explicitly belong to 4Kids any longer, that's probably all the more reason why he could be signed to stay on as Eggman.