It’s simple: you have to be a somewhat likeable guy to win the Heisman.
Think back on the people who have won the award. None (at the time) were considered jerks by the sports media. Maybe later, their bad sides were revealed. But not while in college.
It takes a lot of media work to win a Heisman. The candidate must be patient, show up on time for interviews and come across as a nice person.
It won’t necessarily help you much if you are a good guy, but you will be hurt if you are a bad guy.