WWE knew they need to create new stars. they tried to push Ziggler, gave him opportunities to defeat Jericho, Cena and win at Survivor Series.
You´ve got to be kidding me. That wasn´t a push, that was ruining Ziggler while he had everyone´s attention, to make it perfectly clear that he will never get a real push.
Survivor Series was a completely fucked up match, and was changed several times. There was almost no build-up, and which little there was, was actually about the initial match of Punk vs. Foley. Was there even a promo between Foley and Ziggler?
Ziggler/Jericho was about "not winning the big one". Well, Ziggler lost the PPV match, and given his history up to that point, actually made himself look like the guy who couldn´t win the big one.
Then Ziggler is telling off AJ in the locker room, having a bathroom brawl with Cena, and the resolution is that he was just jealous, got covered in shit in the middle of the ring, and lost to Cena quick and clean after two interferences and hitting all of his finishers.
You don´t ruin someone´s credibility in a dark match, you do it when the world is watching.