Sting's WWE debut at Survivor Series last night wasn't actually planned the way it went down. The original plan was to do an "unveiling" promo with him but those plans quickly changed when creative could see his benefit to a much bigger angle.
Having Sting return in the manner that he did also benefited the WWE Network which a lot of viewers signed up to during the free subscription month of November. This huge angle helped cement in viewers mind that anything can happen on WWE Network which will hopefully translate into more subscriptions in the months to come.
WWE also announced Dean Ambrose vs. Bray Wyatt match at TLC and the live Steve Austin podcast with Vince McMahon hoping people will stay with the Network.
In terms of the night itself, Sting debut was still scheduled to happen before or after the Divas Elimination match, however this was changed and might have been a way to keep an already leaked angle a little bit of a surprise for the maine event.