I don't think Satoshi's the only person that was mining when bitcoin was released. They had cohorts and companions who he gave access to mine for testing purposes such as those listed by Mia Chloe, and furthermore, it was not through mining that he was able to create the blockchain metaphorically speaking, it was through people holding it one after another, until such a time occurred where everyone just agreed bitcoin's this valuable (which it is), and made mining the gold mine that it is now.

As a bonus, I don't think bitcoin's gonna die soon as everyone stopped mining, even if there comes a time where people just got tired of mining and stopped altogether even before all bitcoins are gathered. We have a lot of coins in circulations, approximately 3/4ths if I'm not mistaken, we can cycle that amongst ourselves and effectively create an economy which will definitely diminish bitcoin's monetary value, but at the very least it would make bitcoin a full-fledged currency that will stand the tests of time, so long as there's internet of course.