1. A lot of the discussion at the moment is about action within the USA, Europe, Brazil and China. These are not poor countries. Brazil isn't doing great but is a significant economy. China is taking a lot of action already to move to greener tech. There is an acceptance amongst most that the richer nations should be doing most to tackle climate change, as well as helping other nations.
2. Green does not necessarily mean expensive. Look at the levelized cost of energy in different countries and green options are often cheaper or comparable to fossil fuels, even before the indirect costs are considered.
3. Green is often also the most practical solution for developing countries. In many, solar and wind are used as the infrastructure for power distribution does not exist, is incredibly unreliable and/or very expensive. For a lot of these countries localised green energy generation is a key factor for development.