Phasing out CFCs was much easier to do because CFCs do not make up the backbone of the global economy the way fossil fuels do.

There were some hacks in the aerosol and chemical industries who tried to deny that it was a problem (the chairman of the board of Dupont declared that ozone depletion theory was "a science fiction tale...a load of rubbish...utter nonsense"), but they were small fry in relative terms.

The bottom line is that too many powerful peoples' wallets are lined with money earned by burning fossil fuels. That's why there is no Montreal Protocol for carbon dioxide.