One, they've been heavily propagandized for decades by oil companies. The whole "in the 70s scientists warned of a coming ice age!" and "junk science HOAX!" bullshit. Part of their belief is the contrarian "if democrats believe this, I believe the opposite" stupidity that's become common. Also, since they're reactionaries, they loathe the idea of anything changing, so they fear "they're taking away my gas guzzling truck!" or "I don't WANT an electric chainsaw!".