Satoshi knew that fiat was a bullsh*t system which is why he created bitcoin in the first place. Gold is the only true store of value, and bitcoin is digital gold. No idea what fiat is..
Absolutely there is no doubt about this, Bitcoin will eventually become our digital gold in the nearest future, but fiat still has a great role to play in this industry. For now, until government dealers another mean as legal tender, there is no gold without fiat and there is no Bitcoin too without fiat.
For everyone to get gold, fiat must have exchanged hands while this is also applicable to Bitcoin too, that is why satoshi never created crypto to compete with fiat but rather serve as an alternative payment tool to fiat, so there is no competition here, bitcoin is just a way to simplify the difficulty fiat has brought to its user as regard payment.
both will always be side by side, bitcoin will not be valuable if it cannot be converted to fiat, so also gold without fiat gold will not have very valuable value.
Therefore, before creating this digital currency, Satoshi certainly had his own idea that bitcoin would not replace Fiat but would make it easier for users to make alternative payment transactions using Bitcoin through the internet