Unfortunately there are a lot of people who go through life uninterested in politics and unaware of policies. From the interviews I’ve heard Brady sure sounds like one of them, not outspoken on anything beyond football. It’s easy to shake hands with the devil when you don’t know the devil exists.
To a lot of people, prior to his entry into politics, Trump was just a name, he branded himself as the successful millionaire, undoubtedly Brady believed that con too. I’m disappointed he befriended Biff, but I can see him being invited to some “gala event” at Trump’s behest back in the early 00’s and being excited to go-- and suddenly he’s invited to all Trump’s events. Hillary and Donald were friendly at one point too, did she know he was the devil then?