They've got $400bn+ in annual revenues, with $50bn in free cash flow, and the ability to raise enormous piles of debt if they needed it.

They've not got a pressing need for the cash, so can afford to take a multi-decade view of SpaceX. If you look at other investors who take a view across that time horizon, you'll see some pension funds and huge trusts putting money into SpaceX for the same reason.

It's overpriced today on fundamentals, but in 50 years time, today's price will look cheap.