I believe Satoshi was working on this idea for quite a while...looking at the code, I don't think this was something he threw together in a couple months. I think he may have been working on it for several years and took great pains to ensure it was sufficiently evolved such that it wouldn't simply die shortly after its release.
Everyone has their own belief in something that Satoshi creates, but I just think that although Satoshi is working on this idea for time but at least what Satoshi has created is able to change many lives for the better than ever. With the bitcoin in this world many people love and trust so they can follow it in order to seek profit.
I'm sure thanks to the trust of many bitcoins forever will stay alive because the popularity of bitcoin gets brighter and better so it will not just die.