Being a rabid climate-change denier is a right-wing shibboleth at this point: to be a "good member of the tribe" and especially a leader, there's certain virtues (vices) you need to publicly signal if you want to cling to power.

This is just one of them.

Smith et al know the science is settled. If you gave them a shot of truth serum, they'd freely admit it. They just have to go through the motions, or else some even more rabid proto-fascist will push them out. This is what spending the last quarter-century engaging in pure identity politics, victimization and rage-farming has done to the political right.