Tough judging his win rate like that (and its actually almost 38%). He's managed bottom half sides.
Im not sure how well any manager would do managing that Saudi Sportswashing Machine side in those circumstances. Them finishing 12th and 13th is like us finishing 5th or 6th in my opinion. And while you're right, 8m is an obscene amount of money, it is the going rate for PL managers so he's entitled to it. I also wouldn't underestimate the effect of being publicly abused for 2 years. Can't be nice to be a figure of fun and to have your family watch it?
Most people struggle to take any criticism in their work. To take what he's taken, particularly recently, shouldn't be underestimated.