I’d imagine there are benefits to them in that it weakens their enemy, because either Wagner loses, and therefore Russia loses the forces they represent, or they succeed, which would mean uncertainty and chaos among the regular army during the transition. There’s also potential for Russian forces to be weakened anywhere that Wagner was holding and removed troops from, or anywhere held by troops that get redirected to fight them, and off course that this will mean Russia takes losses and spends equipment fighting itself instead of Ukraine.