We know why.
In the US, the right has taken concerted efforts to hide and distort climate change science for decades. And they've added it on to their knapsack of identity politics.
Believing the science that backs man-made climate change is for women, gays, liberals, and Marxists. You can't have a beer with any of these people therefore there's no climate change (or it's natural and not influenced by humans).
Where Republicans have successfully bamboozled their base is rooted in religion; part of the unfortunate Creationist vs. Science schism that remains more steadfast in this country than others. The most deeply evangelical faction of Republicans are defensive because of the disruption science has exacted on their core values. This is an inevitable progression of understanding and truth, but they aren't wholly without valid reason to be perturbed.
Part of this is the reaction to a prostitution of science by social scientists and pseudoscientists in white jackets; the same well-meaning psychiatric idiots who have tried to classify transgenderism as purely normal and not indicative of a mental disorder in the DSM, for example. Like many mentally ill groups, the struggle should be to remove the stigma associated with the mental illness, not to remove awareness that there is a mental illness in place, and the concern with how best to treat or address underlying causes of the symptom.
Less religious Republicans are skeptical that climate change is as bad as it is made out to be, and that is rooted in a history of valid concern with regard to dunce environmentalists mucking up business without understanding things that concerned them. My home county is a great example. When I was a child I remember they shut down the #1 employer in the county, a lumber sawmill, because they believed it was connected to the increasingly endangered Spotted Owl. It was part of a wider effort in the Pacific Northwest to save the bird. I didn't understand why all the kids at my school were so scared and bummed. I was a kid. I didn't appreciate the impact it had on my community.
https://www.nytimes.com/1990/04/28/us/10000-are-expected-to-lose-jobs-to-spotted-owl.html
Turns out the nature "experts" were wrong, and the nincompoops didn't understand what was causing the owl's numbers to dwindle. It likely has more to do with the natural predator, the Barred Owl, and possibly also pesticides or poisons using in agricultural, including illegal agriculture like marijuana farming that wreaks massive havoc on California's environment (particularly our water). Truth is we don't really know, still. So they put over tens of thousands of people out of work in the late 80's and early 90's, some of the best blue-collar jobs, then they conserved a whole bunch of land disallowing commercial development of for industries like logging, not to mention cattle ranching, and they did nothing to spare the owl...because they
didn't really understand what the fuck they were talking about. Good show!
Generally, I think the EPA is a great force for good, but it has also been a clumsy idiot. Now we're starting to explore how much of this federal environmentalism has resulted in brush overgrowth here in California, and how that has contributed to our wildfires. One of the reasons the Bundy family incurred so much sympathy in rural areas was because how many cattle ranchers know what it's like dealing with sophomoric red tape from bleeding hearts powering agencies like the BLM who imposed their rather silly desire to protect the Sagebrush Grouse at the expense of cattle grazing. That doesn't justify welfare ranching or anything else the Bundy's did, but these valid seats of disgust are what yoke people in the country who actually grow all that food you city folks eat, and know what it takes to do it. I don't care about the Sagebrush Grouse, or preserving it. I care about preserving Salmon and the Bluefin Tuna. Why? Because I eat them.
A combination of these factors negatively influences the perception of climate change here more negatively among Republicans who tend to hold more grounded, practical, pro-business positions. On the one hand, you have well-meaning experts who understand quite a lot, but not enough to really understand what they are talking about, and on the other, you have mentally deranged bleeding hearts like those people at PETA who care more animals than they do about people. This sows doubt.
On top of that, we have allowed our scientific education at the primary & secondary level to erode horribly over the past 30 years because we don't have the spine to tell parents their kids are getting failing grades because it's what they earned. There is a noble American desire here to not let school performance dictate someone's future, the way you observe in too many Southeast Asian cultures, when obviously school shouldn't define your life, which I perceive as a blue-collar capitalist sensibility on the right, and this got married to the liberal "every child is a snowflake" attitude, as well as their desire to neutralize the advantage of social capital wherein wealthy groups' kids (i.e. whites) tend to do better in school, and the deformed baby from these good intentions has been our approach to education where we constantly lower standards; reflecting the same canker you are observing with women and basic training minimums in the military.
So I always find it funny when liberals act so surprised that the Republicans who are extremely wealthy, and don't care about the environment, are able to deceive their base into believing this is another false alarm. The truth is the often irrational, clumsy, and destructive history of the American liberal platform has played a strong role in tilling the soil for these seeds to be planted.