A lot of people think that Trump does not sincerely believe the things that he is saying, and furthermore that he not the best messenger. However, at his most incoherent there are people who vehemently agree with anything he says because they think he is a "winner".
I'd guess that anyone who already thinks this is an outrageously bad decision isn't going to change their mind because they dislike this messenger. As for the others, they seem unpredictable when it comes to what works or doesn't work with them. Maybe they think he's implicitly credible as a rich guy who isn't sentimental and doesn't make an effort to be portrayed as a do-gooder.
I'd guess that anyone who already thinks this is an outrageously bad decision isn't going to change their mind because they dislike this messenger. As for the others, they seem unpredictable when it comes to what works or doesn't work with them. Maybe they think he's implicitly credible as a rich guy who isn't sentimental and doesn't make an effort to be portrayed as a do-gooder.