I don't think he is called that for any particular reason. His fellow politicians viewed him as a goofy dumb Cowboy so they called him "Bingo Bob." If he did earn that nickname in some fashion the writers have yet to reveal it.
The episode where he is first mentioned only make reference to the fact that he is perceived to be in the pocket of mining interests and is not particularly swift on the uptake. But no actual source of the "Bingo Bob" moniker.
Call me fuckin' insane if you must, but I thought this was much better than any of the Matrix films. Loved every minute of it, but I do agree the loom of fate was, maybe not retarded, but definitely not as easy to swallow as a precog or something.