The reason ex-wrestlers are commentators :
They usually choose someone who is "over" with the fans, ie. evoked a reaction whether they were the good guy or bad guy. Anything the good guy says, most of the fans will instantly take it as fact. Anything the bad guy says, they'll instantly think the opposite just to spite said person.
To add to that, the vast majority of non-wrestler commentators are awful. They even tried people with american football backgrounds and stuff, and that was a disaster too.