Because they know that the vast majority of people advocating for climate change to be a high priority issue is because they want to use that to slow down capitalism - the system that made the US the country they love.
I never hear growth-minded solutions for climate change: Let's get rich enough so everyone (even European hotels) can afford AC? Drug companies make enough money so even poor Africans can afford medicines and theraputics? Deregulate the solar industry? Reduce regulatory barriers for autonomous vehicles? Fast track nuclear power? Stop the fight against ride-sharing?
If the problem was climate change & it was a severe existential issue, I'd assume you'd support all of the above?
I feel like that's something you want to believe so that you can dismiss legitimate concerns about environmental destruction.
Because that's like saying capitalists want to grow the economy faster to destroy the environment. Which is obviously crazy and untrue.
I love capitalism. I'm also deeply concerned the way it's run currently will destroy the world my children will inherit. These aren't contradictory ideas. Why can't we capitalism better?
I don't know what you love and call capitalism but I suspect you've been convinced that as a system it has some inherently moral dimension. It does not, and cannot. It's a paperclip maximizer, that's all.