This science research is very, very expensive costing many billions of $$$ on an ongoing basis. Regular charity is a "drop in the bucket" for this kind of research which should be paid for by governments anyway. For health, total spending was $3.8 trillion this past year. Spending more money on health research could have significant ROI in terms of reducing the growth rate of that bill.
And for those who didn't see the live presentation, they all made the point that the biggest story here was that they hoped this announcement would galvanize the community in order to drum up more attention, excitement and thus money.
As an example, many of the big pharma companies have already or currently are pulling out of the psych field. If this huge investment jump starts more researchers to go into this field instead of something else (e.g. cancer) it could create a positive feedback loop.
