Also why would developing countries have to limit carbon emissions more than non developing ones?

Exactly. The cumulative emissions of the United States dwarf the rest of the countries in the world[1].

The powerhouse that is the United States was built on the externality of carbon emissions. Now that the West has built their economies of this externality, they're trying to prevent developing nations from catching up by utilizing the same externality.

[1] https://www.carbonbrief.org/wp-content/uploads/2021/10/The-2...

It's because they're industrializing, have higher population growth, and are primarily building coal power plants to keep up with it.