He can't just dedicate it to this or anything else in one go. That wealth is largely paper wealth based on other people's idea of what he can deliver, but then

He can't just dedicate it to this or anything else in one go. That wealth is largely paper wealth based on other people's idea of what he can deliver, but then he has to, you know, deliver -- if he suddenly dedicated himself entirely to non-commercial projects, then he'd suddenly not be all that rich anymore. So, he has to make SpaceX more clearly a success before he can dedicate any capital to a space-based radiotelescope. And even then, he can't use SpaceX's capital -- he has to use his own.