Because he stopped being financially advantageous to them, and with the Marvel vs Capcom series being down the toilet they probably took this as a moment to axe him without experiencing any pushback.
I hated Ryan Ramirez during the MvC3 years, particularly for his brand of trash-talking and highly unsporting behaviour, but even I think this is a disingenuous move. If there was an opportunity for more money to be made out of him, they would defend him until the cows come home. No doubt Sonicfox could easily coast by on making similar offences without anything being levelled against him.