“Driving people back and forth all night?” A caucus is like a mini convention. You show up at a certain time, discuss issues and rules and try to get others to vote for your candidate and you’re there for hours. It’s not like voting in a primary and going home right after that.
They usually take 2-3 hours. So its no big deal. You drop them off and then pick them back up few hours later. Limo services do it every day. If you were Trump would you spend 300 hundred grand or so to win the Iowa Caucus? Sure you would. I’ll bet that’s exactly what they do too.