You get to keep only enough to maintain a very modest lifestyle in a low-cost-of-living area, the rest of it has to go towards improving the world in some way.
Edit: Given the previous rules that you must maintain a very modest lifestyle in a low-cost-of-living area, would you rather choose to opt out and not have the money at all?
Thought about this before. I’d build out the high-speed internet structure to encompass all the populated parts of the world (omitting coverage across large swaths of open sea) and provide free, no-questions-asked WiFi internet service to absolutely everyone.
(Yes, a lot of places don’t have devices, but parallel programs already exist to get people enabled on cheap devices)
The obstruction would be legal battles with current stakeholders that have regional monopolies and are very addicted to making odious profit. (Looking at you, Comcast, AT&T, Verizon, etc.)