Trump, Pruitt, the Koch brothers and other energy-company CEOs, and the climate-change deniers are all going to be dead by the time the worst effects hit, so they don't care. They made their pile of money, they scored their political points. They'll die happy. What happens to future generations is none of their concern. Those generations can just turn the air conditioning up in their mud-and-thatch huts and build their dikes a little higher is all.
Another factor is composed of conservative Christians who believe, and they've stated it online numerous times, that the worse things get, the closer they are to the Rapture. So, bring it on! is their opinion. Their apathy conforms with their theology.
Lastly, at some point, Obama hurt Trump's feelings and Trump saw that the the way to winning Republicans' hearts was through their mindless hatred of everything Obama, so Trump is determined to destroy every last vestige of Obama, regardless of whether a particular policy makes sense or not.