When you've made yourself a household name by appearing on reality television, it's hard for anyone to consider what you say or do to be anything but publicity stunts. Trump's recent betrayal of Ann Coulter, who was, until now, one of his biggest supporters, is just another attempt on his part to grab a waning spotlight.
Donald Trump has gained popularity for being outspoken and controversial, and it seems to be no difference in this case. He has a thing for opposing many things politically to gain the support of frustrated voters who are tired of the system of politicians that have run the country. An example of an attention-seeking opposition would be his proposal on immigration and needing to "build a wall" to prevent people from entering the country.
Donald Trump is all about being bold, loud, and saying exactly what is on his mind. It is not surprising that he would betray Ann Coulter, who was writing a book celebrating himself, not only to give himself wider publicity but to also giver her book wider publicity and potentially increase her monetary profits.
No, his betrayal was not a publicity stunt. It has more to do with Trump's love of power and his desire to make himself look better than everyone else. Coulter is not the type of person he'd warm up to, even if she supports him. Trump will betray and even insult her because it makes him feel good, because he's that type of a narcissist.