The whitepaper took years to write. Imagine working on something that very few people had interest in for that long.
Probably the most underrated thing about Satoshi was the passion and grit to work ...
The grit ran deeper than the paper. Satoshi told Hal Finney in November 2008 that he wrote the paper only after convincing himself he could solve every problem. The project had about a year and a half of coding behind it, shared privately with a select few before going public.