The Glazers had full control of the club since 2005. Yes, they put the club in massive debt, but since then they restructured the financial side of the club and since then revenues have been growing at an impressive rate.
https://www.statista.com/statistics/267735/revenue-of-manchester-united/
Owners are an easy boogeyman to target, and while the Glazers certainly have not been a Oil Prince that have invested massive amounts of money, they've made sure the club has a very healthy economy and it is generating all that on its own, without the need of shady sponsor deals or outright monetary gifts either. For example the owners of Arsenal and Spurs are much, much worse, where they basically have milked the clubs for all the money they can and largely left the managers to operate on a shoestring budget
I have no love for the Glazers, but the mess we are in are not only their fault. The years after they took over, we had one of the best United sides ever, it was when Fergie retired all things went south. Him and David Gill knew how to run the ship, and since then we suffered because Woody is a money man, we have been chopping and changing managers way to much and we are left with lacking structure at a club level and a patchwork squad that is incredibly unbalanced and not worth half the money we bought them for.