1/ WWE is all just a show, and theres a long tradition of completely useless moves dressed up to look more special. Hulk Hogan's lueg drop for example, or The Rock's "People's Elbow".
2/ They're actors, thats why. They're not supposed to take part in fights, and if they are ever attacked, its to intentionally knock them out as part of the show.
3/ Because its a show, and thats how those wrestlers decided to script that fight. Its called "selling the moves".
4/ Because he didn't sell merchandise.
5/ Because he sells merchandise.
6/ Partly because he costs too much, but also because he's really boring, and theres very little they can do with his character except use him as a vbig scary obstacle.
7/ Training, and experience.