His payback to the fans is his entertainment... he doesn't owe us a lifetime career in WWE because we helped make him a star. He made himself a star by getting us to like him, I don't see how it's hard to understand. "Without the fans, Brock Lesnar has no job", you're right. But without Brock, we have a stale product which isn't entertaining. That's his payback.
I doubt the wrestlers hate Brock, they apparently hate him being in the main event. If you're Vince McMahon and you have Brock Lesnar, one of the all time greats wanting to come back, will you say "No Brock, I don't want to have an extra 200,000 buys on the next PPV because superstars will be upset.", or will you say "Please come back, I want you to make me millions of dollars". The fact is, he's good for business. JR, Foley, Rock, Edge, HBK, HHH have all said the same, it's stupid that the wrestlers are hating on him, of course they'd be jealous but if they were good enough they'd be in that spot where Cena is.
Am I happy that WWE is in a state where former stars are ridiculously more over than current stars apart from Cena? Of course I'm not. If I had it my way, they'd be returning to a roster with new versions of Rock, new versions of Brock, new versions of Austins. But we don't, we have one superstar, and that's Cena., He's our Rock, he's our Austin. Why were those named above so famous? They had skill, but not only that, they went up against legends and won. They feuded with the best of the best, and won. I love the old guys coming back if they put over the new talent. You saw how pissed off I was that Rock went over Cena cleanly, that's not how it should go down. But because of the whoring Cena had, Orton had and HHH had, we have no other talent now who's credible enough to push WWE forward. We have exceptional stars in Miz, Ziggler, Rhodes etc, but if they're not going over big stars they'll stay where they are right now.