I don't blame him one bit. I'd do exactly the same. He's getting to play football in a league where most of the foreign players are so good they can play in second gear, keeping themselves both injury free and match fit for their internationals.
He doesn't have to deal with the politics and insane expectations of being at one of the La Liga or Serie A giants, or burning himself out/left on the bench because yet another manager is afraid to drop Casemiro. If he has a bad game, which he never will over there, there's no social media abuse, and he's lifted more silverware than some players do their entire career - Hasselbaink, Reus, Torres, Gerrard, even Harry Kane for the majority of his career.