I hear your allegation; but I can't think of a reasonably plausible way to make it happen UNLESS (as I said) the GM decimates the team by trading or cutting the best players. Now, could they do it as a legitimate part of a rebuilding strategy? Of course. But what may be tanking in your eyes is not in mine. "Throwing" a game (which is the concept behind tanking.... that is an intentional program to lose otherwise winnable games), I don't believe for a second.
So I'd like to know how exactly that can come about.