Try to imagine if all that The Rock did this year was done by someone that wasn't a top face in the past - they would easily be one of the biggest heels right now.
In his short run this year, The Rock feuded with the top face of the company, looking like a complete heel in his ways.
- He was coward like heels tend to be, mostly only feuding via satellite.
- His arguments were completely hypocritical. He called John Cena childish, but he was the one that was only making jokes and childish taunts all the time, while Cena was actually talking some sense sometimes (like arguing that The Rock has been away for years, while he has been bursting his ass every single week for the company and the fans).
- He interfered in a WWE Champion match on the main event of Wrestlemania.
- And now after a successful tag team bout with Cena, he was the one that resorted to post-match attack.
I find it interesting how much heelish behavior The Rock can get away with and still be cheered like only he does. This does speak a lot about how much he represents.
Well, yeah! Have you ever tried to make fun of someone and NOT be a jerk? It doesn't come off as being very funny, or entertaining. The Rock talks smack like no one else. That's why everyone likes him.
When you're going to talk smack about the most disliked face of the company in it's modern history (and make no mistake, Cena may be the deserved face of the company and extremely over with the fans, etc, but at the same time he is still the most hated too, that's what gets the debates about him so heated because both sides have a legitimate point) you're going to both be liked and come across as a jerk.
However another reason people love the Rock character is that every now and again you see a smile, or a raised eyebrow, or something that's out of character for The Rock, and is a recognizable sign that Dwayne is just having fun with the guy he's talking to. Like how The Rock always teased Lillian Garcia about how she knows about the strudel every time he'd cut a promo in the ring and Lilian was ringside. He was teasing her simply to make her laugh, and while his words, taken at face value were grounds for sexual harassment, the look on his face showed it was nothing more than an inside joke between the two.
It's the dichotomy between Dwayne Johnson and The Rock that so many people like. Perhaps not his smarky wrestling fans so much, but you know? Normal people. They like that kind of thing a lot. It makes them relatable and seem like a guy they could really have fun hanging out with in real life.