That's not really how it works with endorsement deals in the gear industry unless you're making a huge move up or down, not a more lateral move like this. I should know, I have a bit of personal experience with it.
There's a pretty stock/standard artist deals that most of the big companies put out there. For everyone but the mustaines and hammets and claptons.
I sincerely doubt fender lost him as an endorser because esp offered fucking joe from gojira "the big bucks" or something, that is pretty reductive and massively overstating his celebrity.
Is it possible esp thinks he's a bigger deal than fender does so they're going to give him more free shit? Yeah, it's possible but I doubt it honestly.
I think it's much more likely fender/charvel refused to do something on his models (like the Ibanez/everyone thing mentioned) or that he had a behind the scenes personal problem with someone