The Miz won the WWE Championship in 2010 after cashing in his MITB contract on Randy Orton. He went on to defend the WWE Championship in the main event WrestleMania XXVII against John Cena. The Miz ended up retaining the WWE Championship after a little help from The Rock. This was done to set up The Rock versus John Cena the following year at WrestleMania.
Jim Ross spoke about Jim Ross' decision to make The Miz WWE Champion at that stage of his career and also commented on The Miz's match against John Cena at WrestleMania XXVII:
I don’t really know because Vince made that decision. And for me to think as Vince does would be scary. I would say it was a gut feeling that Vince had developed to have enough confidence that Miz could carry his share of the water as the WWE champion. Also, it was an interesting way to get through that WrestleMania and when people left that show, were they thinking about Miz retaining the title or were they looking forward to Rock and Cena? We both know the answer to that. He facilitated, he was a role player on that night even as the champion. I think Vince felt it served a lot of masters at that point in time, but that’s how I would look at it. H/T: 411Mania
Jim Ross on The Miz's run as WWE Champion
Jim Ross went on to discuss The Miz's run and WWE Champion. He expressed why he was not a fan of how WWE booked The Miz during his title reign as WWE Champion:
The only problem I had with that was it seemed like Miz – we took that chicken s**t heel thing to the extreme edges. He rarely won on his own. He never won by gaining an unfair advantage and then winning with a finishing hold or Skull Crushing Finale or whatever it may be. H/T: 411Mania
Jim Ross added that the fact that Alex Riley often helped Miz win, didn't help The Miz look strong. JR added that if the storyline between Cena and The Rock wasn't set in place, there was no way The Miz would have beaten John Cena.
You can check out Jim Ross' podcast HERE.