This is 100% true. BUT...
I respect your opinion, but the problem with your take above (a lot of people have this take) is that this take fails to take into account that not having the Vikings in this media market will help the Gophers to win, and win big.
If there is no pro football team to cover on fall weekends, there will be no doubt be an increase in the media coverage on the team in the fall. In doing so, young football players will notice the Gophers more. Instead of bolting for higher profile programs because they view the Gophers as second-tier, maybe a few high-profile players will stay at home and want to play for the team they grew up rooting for all their lives (this is how players in Iowa and Wisconsin view their teams). In turn, with better players come more wins, which means significantly increased interest in, and attendance at, Gopher Football games.
Certainly this isn't the only reason why we haven't won big in 50 years. However, one cannot dispute that if the Vikings leave it will help to increase awareness in our favorite football team, the Gophers.
Does it guarantee anything - of course not. However, because of the increased awareness it makes it easier. I am all for making things easier on the Gophers to win, aren't you?