It's a good question, and I'm not sure. But I think what it boils down to is they don't want anything complicated, anything that they can't present to their supporters as a situation with an easy solution that suits them. In the case of Trump and Bolsonaro, climate change sceptics/ignorers, they are perhaps averse to publicly following the advice of scientists (or even believing it). Perhaps hard nosed capitalism, making money and letting people do it without constraint, is what their supporters want, and so the thought of telling them they have to stop donig what they want is unbearable for such leaders (even if they believe the danger themselves).