Or, Vince knew the outcome was going to be Cena, wanted to put Ziggler over, made him go from #1 to last four and gave him a promo to give him extra exposure.
I loved the Punk/Rock booking, Punk being the heel, trying to cheat the system and the babyface getting the win for the people instead of having Punk stripped was a great storytelling move.
See: positivity.
Putting someone over doesn't mean having them give an impressive performance with nothing to show for it. It requires PAYOFF. Victory usually, but estblished stars giving props or acknowledgement can work just as well, even better if pulled off right (see: Taker vs. Jeff Hardy).
It requires your top guys to actually, you know, PUT SOMEONE OVER.
Now tell me, how often do we see Cena legitimately put someone over? If it isn't no-selling a DDT on concrete and using the 5 MOD to win, it's making a mockery out of Big Show and Del Rio by calling them phonys. At best we'll get a cena screwjob followed by a "Well gosh golly, I may have lost, but WRESTLEMANIA/SUMMERSLAM/EXTREME RULES WAS AWESOME, EH? EEEEEEH?" cheap line for a pop, where he just shrugs off the events and pushes them to the side.
Cena makes his opponents look worse. Always. People usually never recover from feuds with Cena, or angles with him. Not Khali. Not Umaga. Not Wade Barrett or any other member of Nexus. Not R-Truth or Miz. Not Chris Masters. Not Zack Ryder. Not Del Rio (until his feud with Show/face turn)
There is a consistent pattern in the on-screen product where almost everything and everyone Cena touches turns to shit. He has even downplayed the importance of the WWE title when trying to tie in the fan-respect thing as he feuded with Punk last summer. Edge and CM Punk are two of the few guys who have extensively feuded with him over the years that haven't been buried.
And the last think we really needed Punk to be was the slimy cowardly heel. Should have gone the ruthless aggression, don't-give-a-damn, blunt route.