I just got started with this after seeing it on here a few weeks ago. And so far I really like it

One potential reason posited by The 1619 Project is due to white Americans moving out of metro areas after WW2 in order to "escape" black residents. Then, they restricted expansion of public transportation development to those areas because making them more accessible and usable would potentially result in a influx of poorer, black residents who can't afford a car to commute to the suburbs.

The specific example they used is Atlanta, which has staunch racial lines, horrible public transport, and some of the worst traffic in America. They make a very compelling case.

Here is the relevant New York Times article about it and it's Chapter 16 in the actual book