Isn’t it the same thing as when a candidate drops out or loses? Pay the campaign bills, close the books and the rest is theirs? I think a lot of people run with no chance of winning just to see how much they can make in donations.
Some candidates do run to get donations. Pat Buchanan from us taxpayers.
But professional campaign consultants talk others into running so the consultants can get another gravy train. eg Ben Carson.
There were 17 candidates because there were 13 consultant groups who could talk a candidate into running when that candidate had no chance. e.g. Mike Murphy-Jeb Bush.