This is a huge part of it, plus, once you get outside the top 15 or so clubs by revenue in Europe, the price of transfers (and wages) goes down immensely.Spanish teams are also much better building good sides with tiny budgets than English ones. Even tho obviously the Spanish pool player is better and way less expensive. Villarreal as the budget of a team like Sheffield for Christ sake
Also, Villareal's coach has experience in this competition and is a much, much better manager than United's, so he's getting a lot more out of the total talent of his squad.