The premise is based on the idea of solar geoengineering via stratospheric aerosol injection.
Past that point, the risks of catastrophic climate change spiral out of control.
Surprisingly, the diamond dust crushed the competition staying finely distributed without coagulating and sticking around for a while.

Sulfur, one of the more practical options being considered, tended to clump up more easily.
There are also obvious economic hurdles given the exorbitant price tag.
As already mentioned, it’d be significantly cheaper too.