Are you just thinking about Del Rio? If so. . .then he is the only one ever. Allow me to refresh your memory in case you forgot.
I'd say that you need refreshing more than anyone else me old china
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Hulk Hogan has won it twice (back to back years). After which, Ric Flair won it. Neither of these wrestlers needed a push. This was 3 of the first 5 years they even did that event. Bret Hart won the one after that (once again, he did not need a damn push at the time).
So, are we forgetting Yokozuna winning it in 93 then (and the fact Lex Luger was the co-winner in 94 with Bret Hart) Yoko did need the Rumble win to set him up as the monster heel challenger for the World Title match at WM9. Hogan winning his 2 Rumbles is irrelevant as, when he won them, there was no prize for winning the Rumble. Plus, I seem to remember how excited everyone got over the Hogan and Warrior showdown in the 1990 Rumble.
Shawn Michaels won the next two after that! Though arguably that first one was a big push for his solo career. Second one was not.
HBK's first win was an important part of setting him up as a main event guy (and paving the way for his successful face turn). His second win was to set up a match everyone wanted to see at Mania (even if the match was a let down). Seeing as the winner got a main event slot at Wrestlemania, and WWE was suffering (still) in 1996, surely it's logical that they had the Rumble set up their biggest match of the year?
Stone Cold won the NEXT two! Once again, are you seeing a trend?
Erm, in 1997 Austin was an "up and coming midcarder". He still wasn't main event and wouldn't really be until after his match with Bret Hart at WM13 (which, ironically, was helped along by the Rumble win). Again, in 1998, Austin was the hottest star, the whole Rumble was around him against the whole roster...logic dictates that the man needed the win to set up the event that revitalised the WWE.
Thne after that we have Triple H winning one. . .and more recently, Rey Mysterio, Undertaker, and then both Cena and Orton won Rumbles on back to back years then Edge gets one (yet another face who didn't need a push) before Del Rio cheaped a win this year. NONE of these guys needed pushes at all.
I skipped past the Vince/Rock and Austin wins because, as was clearly the case in 98-01 (and beyond) there was a clear reason for why who won it did. Vince's win in 99 set up a monster buy-rate for Austin Vs Vince in Feb. Rocks (disputed) win set up the 4 corners match (and they did attempt to try help Big Show become a main eventer because of the Rumble, even if it failed).
How comes you didn't mention Benoit's win? He needed the win and it pushed him to main event level (even if he didn't have the charisma to hang there full time). Oh, because it goes against your logic.
Again. . .Stone Cold has won it THREE times during his peak popularity. Rock has won it during his prime. HBK won it back to back times. Hogan won it back to back. Flair's won it. Bret Hart, HHH, Cena, Orton, Undertaker, Edge. . .seriously. Every top face has won the damn thing at some point. Only like 3-5 "heels" have ever won it. This year, it's going to be another top face winning it yet again. I'm going to assume it's going to be either CM Punk, Sheamus, or perhaps Randy Orton if he doesn't have the title at that time. It's always a top face winning it with almost no exceptions. And it absolutely is not an event used to push upcoming stars. If they do that, then it's new.
You don't remember that Kevin Nash became a star because of how he performed in the 94 Rumble? That match set him on his way.
The Royal Rumble is quite clearly marketed as "the beginning of The Road to Wrestlemania" and, as such, it's used as a vehicle to get their top stars positioned for a top match at Wrestlemania. Why would you risk damaging the biggest pay day of the year by giving the win to someone who wasn't gonna be a huge part of it? They have the rest of the year to push upcoming stars (and they have been doing a bad job of that admittedly), Rumble is where the guys that bring the biggest audience interest start to go even more to the front of the line.
And, I don't think Jericho will win it because, quite frankly, he doesn't need to and it doesn't set up a "money" match. I'd rather he came back and had a feud with Punk because that would be good for us IWC fans at least