The TL;DR version is basically this: Marty wrote a bunch of music for Destiny, and Activision wasn't too enthusiastic about releasing his works as an album. That lit his first fuse to his bomb of anger. E3 came around soon after, and Marty was ensured that a specific theme that he wrote would be used in the main trailer. Instead, Activision replaces his theme with their own musical choice. This dented into Marty's pride of his work, and negatively reacted against Activision, maybe too much in some folk's eyes. Activision, being the big douches they are, said to Bungie that if he didn't shut up, their contract may be at risk. So Bungie just flat out fired him, and without his proper pays. That's where Marty sues Bungie for his earned money that they so greedily tried to keep. Marty then won them in court, claiming his approximately $125,000 and keeping his spot as a stockholder, which means more money for him. That's the basic version, anyways.