The worst thing that ever happened to fixing the pollution was calling it climate change. Making wildly inaccurate hyperbolic documentaries and politicizing it to such a degree that it became a defining aspect of our species. Where everyone needed to have an opinion on it, no different than their favorite brand of cereal.
When greedy selfish people make doomsday prophecies which happens to make them more money, the people get skeptical. We've been exposed to millions of such prophecies in the past, the average person will just say "Oh? Another one..."
Regarding Brexit/US election, I think Obama interfering with peoples choices by telling them what they should pick hindered one side in both events. Brexit and Trump happened because Obama was condescending. Both would have been different results if he had done nothing at all.