Man Utd didn't outclass their rivals like City. There were a couple of seasons they should have not won it. 95/96, 96/97, 98/99 and 2002/3 stand out the most.
I don't think City should really win it this season either to be fair, I think they've been poor by their own standards. Arsenal also should have won it last year, just absolutely giving the title to City by the end. Capitulation thy name is Arsenal. But my point being bud, City have spent, but so has Arsenal and especially United & Chelsea. Nobody got near United until Arsenal got Wenger and he settled. United had it their own way for years & years & years and it solidified their stature, the second biggest club in the world. Blackburn, Chelsea, Man City & United all spent heavily to win leagues. The outlier being Leicester, of course, and Liverpool, who spent but no where near the amounts of the others, especially net spend. Arsenal did well under Wenger, I used to love watching them mate, but they've certainly spent a bomb recently. Wenger & Emery never got Arteta's financial backing. Would love someone like Aston Villa to win the league though, maybe even Spurs... Don't think we will ever see anything like Leicester winning it again in our life times though