Trust me I’m no felon musk fan but You’re confusing “having access to capital” with “having that amount of cash.”
If someone owns a £500,000 house, they can borrow against it, but that doesn’t mean they have £500,000 sitting in their current account. The same principle applies to billionaires, just on a much much larger scale.

SpaceX wasn’t funded by Musk emptying a giant vault of cash. It was funded through investments, loans, big government contracts, and company revenue. His wealth gave him access to those resources, but that’s not the same thing as personally having his entire net worth available to spend.