That’s what NBC negotiated with AT&T Broadband (which later was bought by Comcast) in 2001. You answered your own question: it was thought that channel position mattered and 3 was the lowest available. It might also have helped that it was “next door”, so to speak, with KRON on 4. I suspect that most people in the Bay Area, even in the eastern edges, wouldn’t have known what KCRA was. A pretty reliable principle is that, given a choice of network affiliates between a big market and a smaller market, people will gravitate to the station in the bigger market. Vacaville and vicinity in Solano County might have been an exception, but in the vast majority of the Bay Area, 3 was just another position in the channel lineup.