[mrguyorama]

Other than having fairly wealthy parents and family?

His payoff from paypal is not something most people will have access to. The dot com boom was basically a lottery.

[qwytw]

Before Paypal he sold a rudimentary yellow pages search engine to Compaq for $305 million so that they could merge it into their search engine.

Compaq managed to sell AltaVista for $2.3 billion 6 months later and not long before the crash so maybe it wasn't the stupidest move on their side.

[googlryas]

How wealthy were his parents and family? How many other people have parents and family that wealthy, or wealthier? How many of them end up being $100+ billionaires?

[Chris2048]

Many people are "fairly wealthy", yet don't end up as billionaires e.g. many doctors, lawyers or SWEs.

Elon family riches is uncertain: https://futurism.com/elon-musk-dad-emerald-mine