SQL is not the name of a piece of software, and SQLite is developed by a single person.
While SQLite is developed by a very small team[1] and does not openly accept patches[2], it is not developed by a single person.
1: https://www.sqlite.org/crew.html 2: https://www.sqlite.org/copyright.html
From the link, it appears that it was developed by a single person in 2000, who then brought on board 2 other people as contributors in 2002 and after.
That’s probably true but building a clone that people understand, even if slower, is extremely valuable. Understanding an existing technology deeply is a gateway to innovation.
That said, SQLite is so remarkably stable, lightweight like a feather, and incredibly battletested, that even a hypothetically superior alternative would have an immense uphill battle to reach the same value prop.
Still cool as a hobby project.