I remember someone on this forum years ago arguing that someone (Mattingly?) deserved to be in the Hall, partly because he had more "MVP Award shares than Babe Ruth."
Ruth is 100th in Award shares on bref; Cobb (1 MVP in 24 years) is 181st. https://www.baseball-reference.com/leaders/mvp_cya.shtml
It's kind of like arguing that Lamarr Hoyt was better than Cy Young himself because he won more Cy Young Awards.
This is something I've gone down a deep rabbit hole on a few years ago. I've never found any really specific details on the rules, but my best guess is...
I think it goes back to the MVP originating as the Chalmers Motors award, where the winner got a car. There was a rule against repeat MVPs for that (how many cars do you need in 1910 anyways?) and I guess that when that company went under and MLB took over the award, they kept the rule for some reason.
It wasn't a rule everyone on the MVP voting committee followed, because Hornsby finished 3rd in '27 after winning it in '25. Somehow though, Ruth got 0 votes for his '27 season.
And actually, I'm wrong above -- Walter Johnson was the first to win 2 MVPs, though the first one was the Chalmers and the second was the MLB award, and I wonder if the MVP committee didn't consider the Chalmers award to be a real MVP...
And if you've never read about the 1910 controversy, enjoy: https://tht.fangraphs.com/the-chalmers-award-had-a-memorable-debut/