Do you think all of it was Prigozhin’s idea and he did it for free? Whatever. We’ve all got opinions. I was (We we’re) called crazy for believing a lot of things which later proved to be correct.
Prigozhin was shooting off his mouth about problems in the Russian military for quite a while.
I suspect he had reason to believe his days were numbered. That is what he said. The whole monetary setup for Wagner was set to change a few days after the "coup".
Who was in his corner, who he thought was in his corner, and what made him change his mind, are things which are difficult to know and to speculate about. By nature, such support or lack thereof, are very closely guarded secrets.