Some of the IP holders might be skeptical about this game thats probably why they aren't allowing their character in the game. They probably want to see how it turns out, if its good they will probably change their mind.Well thats my opinion
Now, the conspiracy theory? Nintendo (Possibly combined with Microsoft) is concerned about this game's success and had paid Activision/other companies, not to let SuperBot use their characters. Conspiracy theory end.
Yeah I really think some IP holders (maybe even first party ones) don't want their characters being associated with this game if it ends up becoming not that great (although I'm positive the game will be tons of fun) Maybe it has to do with sales too. Hopefully this game will sell well enough that other IP holders well be like oh okay there is an audience for this.
Everyone on here calling Activision greedy probably caused them to turn their backs on this game and not allow Crash in. I think we're being punished
Punishing the people who provide your income is never a good idea, especially when they're prepared to offer you a gold mine.