RE:Literally wtf It does sound like something out of a movie... internal conflict between the Russian Army HQ and this private military group "Wagner".
Perhaps Progozhin felt that Wagner as a whole wasn't being treated fairly, and maybe he's the leadership type that actually cares about his men and how they are treated. From what I've read Progozhin called the some of the Russian Army leaders "evil" so my guess is they delt them a rough hand, to do the heavy lifting so to speak, and then basically left them to eat sh!t afterwards.
If you have a backbone and you feel betrayed then the resulting fury does tend to lead to rash decisions. Maybe they have a chance. Either way it great news for Ukraine and allies.