Seeking approval. It's apparent from everything he posts on X + the memeing + the whole "I am a elite Path of Exile"-saga.

Spreading his seed.

Going to Mars.

Some people are just driven. A friend of mine who failed at a first startup (in a domain in which he had lots of expertise) then succeeded with his second startup: very nice exit but that's not why he was doing it.

He's an action junkie.

In both cases he saw inefficiencies and just wanted to spend the energy he's always been overflowing with to improve things. I don't know about Musk but my friend hates mediocrity and saw everything as something he can improve.

In another case I was in car, for a long trip, with someone else (who was working to become an... Ambassador: hardly the tech type!) and that person would constantly comment on what could be done enhanced.

Something something about personality types, the builders, etc.

Those who only ever want to spend the money of --and benefit from the wealth created by-- others are going to dismiss it all as "people who are after money" but it's more complicated than that and you can't generalize people.

I know several doctors for example: two of them are clearly money-driven (one of them literally told me "I'd never ever teach medicine, I'm in this only for the money") but most of the others I know are just happy to help people be more healthy.

I've got another friend, not rich at all, he's working an additional job as a firefighter: sure it brings some money, but that's not the reason. He's also an action junkie. He was there driving ambulances during Covid: to be helpful, for the action, etc.

It's not all about money. Thinking it's only about money is a mindset that often comes from those who want the money of others (through taxes).