You have no idea why that happened, you are only speculating. It makes just as much sense to me that he'd do it to save his own job, ie, let's try something radically different because the ship is sinking, or because Wade (or Jerry) insisted on something different. It's all speculation and there is no basis to assume a motive.
Especially when if you stop and think about it for a second, there was no reason to sabotage Wade, since it was already obvious Garrett was the chosen coach in waiting.
Yeah, I don't agree with that. I'm not gonna go back and dig through 150 post game press conferences though. But my recollection is that he frequently said "we have to do this better," and I think that includes himself. If you are looking for a "throw himself on the sword" moment, it may not be there, but that doesn't mean he's not taking accountability, it's a rhetorical style that is simply pointless to demand out of a press conference, as again, they are completely meaningless and their only purpose is fan service. Not like Bill Parcells frequently said it was his fault, and he also frequently called out players. It's all a matter of degrees, it's not just black and white like is being stated here.