> This needs investment also. An investment poorer people cannot or do not want to do.

The general premise of investments is that you end up with fewer resources by not doing them.

It now costs less to install a new solar or wind farm than to continue using an existing coal plant, much less if you were considering building a new coal plant, and that includes the cost of capital, i.e. the interest you have to pay to borrow the money for the up-front investment.

Poorer countries would be at a slight disadvantage if they have to pay higher than average interest rates to borrow money, but they also have the countervailing advantage of having lower labor and real estate costs and the net result is that it still doesn't make sense for anybody to continue to use coal for any longer than it takes to build the replacement.

It just takes more than zero days to replace all existing infrastructure.