Well, what did this season tell us?!
That he wanted to leave the team and had to find a way not to be in the top 3 in September? I think it's well known that he was the driver that because of his car control profited the most from the blown diffusor and that it hurt him much more than anybody else to have to adjust to this year's regulations. He was typically already driving with an open wing on turn entry because the diffusor gave him that much downforce to comfortably support his car control. Everybody else wouldn't open the wing until after the apex. And if you have four titles in a row and end up with a weak motor and no support for your style of racing motivation is down the drain. If you then end up being beaten by your teammate it's even worse. If you hear the stuff Marko said in early summer about him being their main cost factor (after having single handedly gotten them eight titles) you know there was no love anymore between Vettel and Red Bull as early as June. Doesn't help with motivation either. This season's Vettel will not be next season's Vettel. Motivation goes a long way.