Rail was sold by the city as a way to promote growth there- aside from hooking up the airport, it was the only reason to run rail at all.

The central question is how was the land abutting each station zoned? Did they change the zoning to allow for more development? Or did it remain mostly residential-zoned and just change from single-family to multi-family?

The reason rail works beautifully in other countries is that you can get off the train and walk to useful destinations, even if where you disembarked isn't where you live. Shinkansen in Japan have tons of shopping, nice restaurants, and hotels all within a block or two of the station. So there's a reason for non-residents to stop as well as residents. And because everything surrounds the station there's no point for residents to go anywhere else.