there is a huge difference between fighting in the ring and fighting outside the ring.
Just look at Bob Sapp, no skills but powerfull. In the ring there are rules, in the real world you should be worried that he would smash you into the ground and would kick you into the hospital. No BJJ skills will help you if you are lying on the ground and someone with his weight would jump at you and use his weight. And even in the ring Bob destroyed some highly skilled fighters.
Boxing same deal. In the ring he would be destroyed, in the real world they are enough boxers who get their ass kicked if somebody grabs them and throws them into the ground.
In the ring they are enough fighters would who defeat Ronnie in his prime. Outside the ring, if you are a smart fighter you will try to avoid fighting a guy like Ronnie. (BTW a smart fighter always tries to avoid fighting outside the ring).