I truly believe the Republican party has figured out what PT Barnum knew so well, half of USA are idiots, and they can exploit that. Same reason they are anti education, want to regulate the internet, criticize universities and highly educated people, it's all just a way to pander to the moron vote, and keep a good supply of morons.
I'm sure the ones at the top are well aware of what is happening, as are some of the right wing pundits, they haven't cared about anything but lower taxes for the rich since Reagan, yet half the people keep believing they care about what's good for America.
If Rush Limbaugh had said he believed in Global Warming, I believe the Republican party would have had to accept his opinion, but he didn't so they have to go with what the fat rich man says. By denying what is obvious to 98% of scientists, they can keep their ignorant base in line and praying for a job.