Bitcoin white paper was realized soon after the 2008 financial collapse. I don't think that Satoshi had an aim to replace fiat. Creating Bitcoin was more like an attempt to show that there is an alternative to fiat.
He crested a decentralized one that eliminate the middlemen/government/banks etc. It is secured too, and bitcoin is really a good project where anyone can have control of their crypto currency. You can sent it anywhere inj the world, creates opportunity etc. think cryptocurrency is one of the wonderful creation/inventions that has really evolved and empower anyone who has access to it.