@boner There’s no consensus on his motives. He claims he was attacked by Russian regular forces. He also claims Sergei Shoigu, the minister of defense, lied to get Russia into the war for personal glory, but these are unsubstantiated.
A plausible theory is this is a power struggle between Prigorzhin and Shoigu over the future of Wagner. Shoigu wants to integrate Wagner into the regular armed forces, Prigorzhin wants to preserve it as his personal organization. He may have secondary political goals, such as becoming minister of defense, and then the de facto leader of Russia through control of the army. Putin has strongly denounced him as a traitor, so he is now likely going for the maximal goal of overthrowing the state to ensure his survival, which is unlikely.