I read an interview with him once where he said it was initially supposed to be the “house” version of SimCity, and be about how good or bad architecture shapes the lives of the house’s inhabitants. But their playtesters were spending all their time on the people, not the building, so the pivoted to making it more about the Sims’ interactions.

IME, you can really see the bones of that initial concept in Sims 1; but it’s stayed throughout the series.