I disagree - they don't want to talk policy, they think they can create policy that wins people over, calculating which positions can deliver which demographics. The policy that sells fits on a bumper sticker, easy thumbs up or thumbs down type of stuff. People don't think twice about whether a flat tax is better than a fair tax, they just know they hate the IRS. As far as their true beliefs, I think they all sold those out long ago and they lack the ability to adapt. They pitch their plans and stump speeches so much they are married to them and it becomes a part of them.
Trump knows the details can be damned, he watched Obama get elected on zero substance. Just entertain and hog the spotlight and you will win the popularity contest. People love to hate him.
By people I mean the 98% of the population that can recite more Bachelor participants than Supreme Court justices.