They really don’t. Words have meanings and the US is not the only country in the world. Other countries still have actual conservative parties. The GOP used to be a conservative party but really should not be called conservative any more. It is a right wing populist party with a shrinking centrist wing (that still has some old school conservatives in it) and a growing right wing extremist wing (which has actual fascists in it).
He did that because he needed the money. He was in a very precarious financial situation in the early 2000s and probably would have gone bankrupt without this gig.