Was it a "George Lucas/Star Wars prequels" type scenario where Roddenberry had full creative control, and thus full accountability, or is it less clear than that and Roddenberry was simply a scapecoat? And was the perceived failure of TMP simply a convenient excuse for the studio to ditch him, or did he really helm the project and thus was accountable for its (perceived) flaws?
shareI'm pretty sure Roddenberry had a lot of control, he was an extremely egotistical and stubborn man, impossible to get along with. I've read a few articles in Starlog where the consensus by almost everyone was "get him out of here".
I remember they actually made the sequel because Roddenberry screwed up TOS so bad, they just couldn't let it die such an awful death. After a lot of negotiation they slashed the budget and went out and hired some REAL Hollywood TALENT like Harve Bennett, Robert Salin, and Jack Sowards. Salin replaced Roddenberry as producer and by all accounts he did a fantastic job. He was very loyal to Harve Bennett and wanted to work with him again but unfortunately I don't think it worked out that way.
Back to Roddenberry, yes, it's true the studio kicked him out, wouldn't allow him on the set and he STILL caused severe problems. I think he leaked the reveal that Spock was getting killed off!! I don't hate Roddenberry, I kind of am in awe of him as he was able to change careers several times, the guy had talent but he sure was ornery sumbeeach!