Fossil fuels is kinda a prisoner's dilemma issue. Everyone cooperating to save the planet is obviously ideal, but realistically there are always going to be companies/countries that won't. And as long as it's cheaper to not be environmentally friendly, there's always going to be someone taking that option.

For example, lets say country A passes new regulations on manufacturing to be more environmentally friendly. The new regulations take the country's manufacturing from low pollution to very low pollution. However the increase in cost causes many companies to stop manufacturing locally, and instead outsource their manufacturing to country B with low regulation and moderate pollution during manufacturing. The end result is more money leaving the local economy of country A, and increased global pollution.

It's a similar prisoner's dilemma for the individual companies involved. If your competitor is able to make their product for cheaper because their process is less environmentally friendly, then they can undercut you and put you out of business.