Should States sub-contract war?

I never quite understood why Putin had to hire the Wagner group when it had already what the rest of the world thought, the most formidable army around. 

One’s own army seems pretty easy and direct to control as long as a State’s institutions are strong enough, but when a Head of State puts two competing groups as its defense arms, this might be asking for trouble as one will try to surpass the other, and this is not a desired kind of competition in a war situation, like the invasion of Ukraine. 

Further, the “quality of the ingredients” constituting the Wagner group wasn’t the very best, hence it was no surprise to me when Yevgeny Prigozhin began criticizing the Russian Federation for not helping him, for making very bad decisions or shooting his soldiers.

The chicken has simply come hone to roost, exposing Putin second most blatant error of judgment after invading Ukraine. 

I thought Valdimir Putin was much smarter than that, but his actions might betray just another case of the Peter Principle, this management concept, that states that people in a hierarchy tend to rise to "a level of respective incompetence" as they are promoted based on their success in previous jobs until they reach a level at which they are no longer competent, as skills in one job do not necessarily translate to another. 

In Putin’s case it shows that his KGB education might be woefully lacking in common sense and imagination...