At the moment he refuses United's offer, he has no guarantee at Juventus and he was told quite clearly he was not wanted.The issue is that he doesn't prefer the bench at Juventus, that's in itself wrong. And it's audacious to make that statement when you know the context.
So that option aside, and maybe Spurs, he was negotiating but he was not able to tell himself:
"I have no future here, so I will talk to my agent, and try to find ways to fix the images situation so that I can find a way out".
Instead, he allegedly opted for some sort of status quo by going back to Juventus and eventually, Juventus folded.
There is an expression in Korea for that kind of behavior, when you don't really care at some point and just do it.
Some kind of image where you are proposing the others to cut your belly up, or something like that...
You are speculating he doesn't prefer the bench at Juventus, but if Juventus doesn't find a way to play with him, then the bench it is, and maybe this time it will make things clearer to everyone.