At this point, it's self-reinforcing. One of our two major political parties has climate change denial as a fundamental part of its identity. Lots of people vote for that party because they share that belief. Those who benefit from that party's success are then motivated to spread that belief even further just to recruit more voters to the cause. And as that belief solidifies among their voters, the party becomes unable to change its position no matter how convincing the facts become.
These are the people who Trump wants to set free of all regulation.
Environmental diplomacy is hard, and made much harder by the fact that most tools to stop pollution require such massive cuts to industrialization (and western pollution first) that most countries can't afford to enact what is needed.
So we have had the weak predecessor of Kyoto, and then the even weaker Kyoto protocol. Which has been followed by nothing.
This just means that people are willing to play the game of lying to their populations and voters, who can't care or understand the issues because they have other existential problems to deal with.
Distributed responsibility is another name for "not my problem".
That's part of the problem. There is no "extinction risk," at least with regard to human life, and anyone who says differently is either misinformed or lying. In the latter case, it's easy to argue that they have an economic agenda that has nothing to do with climate.
Either way, such absurd exaggerations make it hard to sell the real truth, which is that AGW appears to be a legitimate problem that demands action.
Its actually not; even if it is an extinction risk, if a meaningful difference in risk can't be made absent collective action, you have a massive tragedy of the common problem in which individual states are incentivized to do as little as possible, except what is necessary to signal that they would be open to serious action if there was an agreement on collective action.