If Mark was an employee who was fired and refused to leave the premises, he'd be escorted off by security. If he promised to show up a few weeks later to talk to the board of directors or investors, they'd similarly bring in security.
That's what happened here (or what he threatened to do, anyway.) After a really bad weekend, he was "fired". Then, over a series of emails with escalating demands he eventually threatened to show up at the project booth falsely representing himself on the project. Yet, he was offered exactly what he'd have gotten if he stayed on the project.
As for the rest, it's probably harder to see this if you've never had to do it before, but it's really exhausting being asked to repeatedly justify your actions in a situation like this.
When you find that one golden person who says, "I trust your judgment", it's honestly shocking. It feels good to have your judgment trusted when you go to someone saying, "Hey, I was in a bad situation and had to make a difficult decision" and they say, "That sounds tough, but I bet you made the right choice," rather than, "Tell me why you did that?"