I don't think Trump being rich is a selling point to most who voted for him.
They voted for him as a 'fuck you' to Washington. He was the first guy in years to say their pain was real, and he'd go in and fuck shit up.
His supporters were/are able to rationalise away traditional political weaknesses (eg him being rich/an asshole/racist/dumb/unstable etc) because the thrust of what he said was appealing enough to them.
Palmer was a similar phenomenon here, except with less anger at Canberra than Americans feel at Washington (still some, we hated Gillard and Abbott), much less of a message and in a non-presidential system he needed to lead a party, which he of course could not lead effectively. The primary process in the US allowed Trump to take over a party.
It was anger at Washington that enabled Trump, nothing else IMO. There was another character who said people's pain was real and we needed a resolution, he ran in the other primary, but he just didn't have fame or financial backing initially and so couldn't overcome the party's long term plan to coronate a particular candidate.