I’m currently reading the book “Game On!” About video game history, and had to verify.
When initially designing The Sims, Wright spent a great deal of time researching the fan community of the hugely successful Quake and Quake 2. “I was amazed at the time people were pouring into making their own custom levels,” he told Wired. “So with The Sims, we wanted to make it possible to modify everything. Players could use it as a storytelling platform.”
https://www.shortlist.com/news/15-things-you-probably-didnt-know-about-the-sims-4
Yeah, apparently SimCity itself was the result of Will Wright working on an helicopter shoot’m up and realising he had fun making maps for it.
That’s an interesting starting point for codifying a whole genre of games.