Bungie wasn't PUSHED out of Halo, they WANTED out of Halo. They had a contract for 6 games, and when Microsoft asked them to renew for a new contract, they were like 'no' because they were sick of Halo and wanted to 'spread their wings' and work on a new IP, move on to 'bigger and better things.' But still salty about having their work continued despite wanting it to have ended? Yeah, they're probably still bitter.