There are large numbers, and then there are even larger numbers.

Academic research is roughly $100 billion a year in the US. A foundation with $2 trillion could support that indefinitely with the required 5% minimum distributions. By today's numbers, the seven richest Americans could fund that.

I don't know worldwide numbers, but 4x the US is usually a good rule of thumb. You would probably need the 100–150 richest people to support all academic research worldwide.