Because he has a one-off fortune that would require selling all of his investments to turn into cash. By 2050, all of the power plants he built would be just so much garbage in a landfill. Based on the growth projections of energy consumption, it wouldn't put a dent in the problem long term.

By incentivizing economical carbon capture, he might be able to kick off a self-funding industry, which would be an important part of the long term set of solutions needed to address atmospheric carbon increases.

He could also do other things like invest in some power plants too.

I partly agree - yes, individual people spending money is not a long-term solution. But we aren’t even in the stage of needing stable, long-term solutions - we need immediate, drastic, dramatic actions. And there are already strong incentives for carbon capture technology - it’s a big and growing market. The bigger bottleneck is not in capture innovations, but in emissions-reduction action, now, here, this decade. So, yeah, I mean, I get why he wouldn’t personally choose to do it that way, and I guess I’m excited about the prize? But man do I wish he would do more.

He kind of has an interest in solar power

The impact that even a billionaires could have is relatively trivial. The Green New Deal is estimated to cost trillions of dollars. Even if some of the proposed ideas are dubious, the amount of infrastructure needed is an order of magnitude more than what a billionaire can provide.

Yeah, I mean the green new deal was like 75% not climate spending? And a billionaire does not need to tackle the whole problem, just make a dent? My main point was that we actually already have most of the technology needed to fight climate change, we just aren’t deploying it.