Yeah same. I think the majority of United fans did back him to be fair, and it was more so the media, opposition and a loud minority of United fans who didn't. For his age he was still incredibly talented, and all his lacking areas were ones that you would assume relatively simply to fix with time.
I think that backing could have a huge say in him sticking with the club. Mata mentioned that when he joined De Gea told him that the fans are unbelievable, even sticking with you when things are tough.