Just think about the actual claim to fame of those 5.
Trump inheriting a real estate mogul and added multiple bankruptcies to that business, but is a successful reality tv show host and can manipulate bankrupcy law to insure he never truly fails.
Cruz, who's claim to fame is a government shutdown which ended up getting republicans nothing in return but unfavorable polls.
Carson, a successful brain surgeon, book seller, and pundit.
Fiorina, a failed CEO who was fired after she drove HP into the ground thanks to a stupid Compac buyout.
Rubio, whose claim to fame is immigration reform which could never get past the house.
Going strictly by resume, Carson, a guy who's never even held office, is still probably the only one that makes sense.