Elon could build 20 St Jude Children's Research Hospitals in 20 countries around the world and charge $0 for services, and, still be a trillionaire.
He could. Yes.
And it would help a lot of children, that's true. But he's thinking bigger than that.
His projects are setup to help humanity as a whole and keep doing that into the future even after his death.
Giving massive help to people directly comes with problems. In general society hates huge changes that affect them. The companies/entities affected tend to fight against it and try to keep the status quo. If he built lots of free hospitals big pharma would come after him with pitchforks and he might end up dead.
You could spend your time/money using your hands to build new houses for homeless people, or you could spend your time/money addressing the root cause of homeless people to try and make the next few generations hopefully the last. Both are nobel causes, one helps people now which is really good, but it only helps a small number compared with the other which helps an almost infinite amount of people in the future. There is no right answer to which of those approaches is correct. You make your own call, they both have advantages and disadvantages. There's never one perfect solution to any problem, there is always many solutions all with their own problems. You pick the one you feel is probably the best option. That's all you can ever do, or be expected to do. He's decided that focusing on the future and long term help is the better option rather than trying to help people right now.
- Kicking off the EV revolution sooner rather than later will already have saved a huge amount of people in the future.
- The transition to robotics/AI will drastically lower the cost of all food and goods because extracting resources and turning them into food/goods wont need expensive human labour, only energy, and it can run 24/7 using batteries + solar or fusion eventually.
- Developing the neurallink technology will drastically improve the quality of life to basically everyone with those sort of injuries or birth defects, children included.
- SpaceX will create a booming new space industry. By making sure humans are well established on multiple planets or in space in the long term, not just on earth, it will ensure no huge asteroid can wipe out all of humanity. A huge asteroid is heading towards earth right now we just don't know if it's in 5 years or 5 million.