Historically commissioners have come from outside the game. Landis was a judge. The next guy was a governor and US senator. There have been several lawyers. Peter Ueberroth (sp?) was the guy who ran the LA Olympics. The whole point of the job was that it was supposed to be an impartial, disinterested, highly respectable man who looked out for the greater good of the game. (It was a major scandal when an owner actually took over the commissioner's office directly, enough that it took years for them to take the "acting commissioner" off of Selig and make it official.)
In any event, since the public had no idea what a weirdo Hoover was back in the 50s, he's exactly the kind of guy whose name would have come up for it.