Typically, when someone creates a blockchain or cryptocurrency they set aside a certain amount of the crypto for themselves and or their company/foundation as tokens for future adoption.
For instance, Charlee Lee mined thousands of Litecoin in its early days because not many people were mining it and he knew how to because he developed it.
Since, he was first he got a large amount of coins and gained millions of dollars worth of Litecoin this way.
Or a coin could be premined – this simply means that all the coins are created and they don’t need to be mined, and the founder could keep a percentage of them for himself.
Regardless, of how it’s done the founder sets aside a percentage of the tokens and becomes wealthy if the blockchain is successful.
Want to know who’s one of the wealthiest people in the world? Satoshi Nakamoto. Satoshi is worth 1.1 million Bitcoin (more or less) which means he(she? them? it?) is worth 38,500,000,000 dollars (7/2/2021). It doesn’t seem that Satoshi intends of spending the Bitcoin (none of it has been spent since he disappeared in 2011) but Satoshi is wealthy.
So can crypto founders get rich? Absolutely. Is it guaranteed? Nope. The blockchain actually must succeed.