Everyone loves Elon and at 46 years old, his investment strategy increased his net worth to over $20 Billion Dollars.
What stands out is that Elon doesn't invest in things that have been known for exceptional ROI. He invests in things that never had a ROI, projects everyone else would most likely stay away from, simply because they seem like they would never ever even survive as businesses. He invests in a future he'd like to see and doesn't care about the probability of success or failure. That's why we love Elon. And because he creates the tech no one else dares to bring to the masses.
This is a piece from an infographic I found that shows his current investments and what industries he's mostly 'betting' on. I had known about SpaceX, Tesla and DeepMind, but had no idea that he was also involved in Jason's Mahalo/Inside (what actually happened to Mahalo?), Stripe and Halcyon Molecular.
Source: https://evannex.com/blogs/news/elon-musk-investing-in-the-future-infographic
Check out the link above to see the full infographic. If you want to know more about why he chose to invest in these companies I recommend to read either his biography (obvious choice), or the posts about him on waitbutwhy.com.