Mathematicians spent decades agonizing about matrix transformations and surface normals, all entirely in the abstract, and then in the 80s that math turned out to be suddenly extremely practical and relevant to the field of computer graphics.

Who pays for this abstract exploration? I get that "in the future" it could be useful, but today these researchers need money. Is it like open source where people just do it because they want to?

The problem itself might not be very applicable, but the techniques used to solve it might be.

That said, researching something solely for the sake of curiosity can be a valid endeavour. Many profound scientific discoveries have been made by researching topics with no obvious application.

Things like this sometimes lead to practical inventions like velcro or self-locking mechanisms that could be useful. All it takes is someone to connect the dots or find a use case for it and change the world in a small way.

Some maths is done just for fun/curiosity and other maths is more directed towards a specific goal. Both types of maths can end up being useful or useless (outside of maths, that is) and it's pretty much impossible to predict which areas are going to be incredibly useful or mere curiosities. Sometimes, the uses for obscure maths aren't even discovered for more than a century afterwards.

I remember someone (G.H. Hardy?) saying something along the lines of "the only bad thing about math is that it can be useful."

George Boole might have some opinions on this.