re: Why are most of these Republicans running?

See if any personality or ideas resonate with other than Trump REP voters.

Looks alot like the last DEM primary. Sanders won his share of early states, and the rest split the vote. They all backed out endorsing JB and he cleaned up on Super Tuesday and did not look back.

DT will very likely win the early state primaries with 30-35% of his party loyal followers. Rest will split the vote. They'll need to determine who is the best alternative to DT (and more importantly who can beat Biden), and everyone will bow out and back that candidate. On Super Tuesday for the REPs it will be a binary choice - DT or XXX. Put it in the books.

Will be interesting to watch unfold and of course hear all the rhetoric between now and then...