Why is mauga almost ALWAYS meta?

I've watched a lot of OWCS recently, and once again its just mauga EVERY GAME. I don't actually hate mauga, in coordinated play he can actually be fun to watch. I just hate the fact that he seems to be always meta and we never see other tanks, and he seems to gatekeep the majority of the tank roster (especially winston who is really fun to watch).

So why is he always meta, is it some part of his kit? If I was to guess it would be the cardiac overdrive which is just too powerful with coordination, and they can't nerf the numbers any more because he'd have an insanely low winrate in ranked.