It's a grift. It's always a grift, and Carson's promoters are some of the griftiest of them all.
One need only look at the Republican candidates from the last two election cycles to see the cycle of grift at work. There was Ron Paul and his newsletters promising to show you how to put all your money in gold in advance of a worldwide economic collapse that never seems to arrive. (But please don’t cancel that subscription!) There was Mike Huckabee, recently busted for hawking a cinnamon-based cure for diabetes to the elderly diabetes-prone conservative base, using his 2008 campaign to land a talk show on the Fox News channel. There was the grandmamma of them all, Sarah Palin, who famously quit the governor’s mansion in Alaska after running for vice president in 2008 because she could make way more money babbling on Fox News occasionally, selling books defending that oft-endangered celebration of Christmas, and starring in reality shows.
As Legum notes, Ben Carson was never in this to win anything. It was all about the grift. I'm certain the same is true of Donald Trump, since he's been a greedy grifter his entire life.