Trump pulled out of the Paris climate deal because he is keeping his promise...Trump made a careless campaign promise but he kept it.
For the apparent 40% who continue to support Trump, keeping the campaign promise is important. For Trump, keeping his base happy is all that matters. In his mind, that base put him in the White House and it will ultimately return him to the White House.
It is also apparent that Trump does not accept, or believe, he lost the popular vote. He does not accept or believe the polling showing his term in office is in the gutter.
Trump laps up the fervent support among his base, ignoring the majority of Americans. He is staying the course to please the base that elected him.
Trump will use this decision to sell himself, to paint a picture of how he keeps his promises...
Trump is a salesperson and keeping this promise is a tool to be used to sell himself to his base.