With something like this it is impossible to really estimate, even if you are looking only at direct effects (starvation. etc.)

First when you have a chain of necessary companents: (Scientific Invention > development of agricultural techniques > NGO Deploying of techniques > Rich guy funding the deployment > ex politician who convinced the rich guy) , each one can claim full credit for the process.

Then you have to guess what would have happened if this guy didn't do it? Would Mexicans still be farming like 1824?

The estimate is nonsense. Africa's population has trebled (or whatever) yet the green revolution never happened in Africa. The continent is overwhelmingly fed on pre-green revolution crops grown in pre-green revolution ways with low fossil fuel inputs. The old ways scaled up. (Though arguably at great cost to natural habitat.)

Certainly there would be many more farmers (less efficient) without this gent's green revolution advancements and the food would be more expensive, but it's baseless to assert everyone would have starved otherwise.