Under "Counterarguments" section it's been argued that the streetcar lines were already on a downward decline by the time GM bought them, so blaming GM seems tenuous.
US streetcar lines were in the 'transit death spiral' in no small part because they were largely built before cars were common, and became dramatically slower once car traffic started obstructing their right-of-way, which they were usually required by contract to maintain.
(There were many other factors, including their overexpansion during a securities bubble and that their concessions were usually for a 'nickel fare' with no inflation adjustment, which lead to declining real revenue over time)
Streetcars, combining the routing inflexibility of trains with the vulnerability to traffic of busses. We could have saved them if we'd banned cars from city centers and you can argue that if you want to but it wasn't GM that did them in.
"Vulnerability to traffic" can be alternately expressed as "right of way violated by individual cars." The history of the decline of streetcars in the US is the history of automotive companies convincing the public that cars take priority over all other forms of transportation, consequences for the commons be damned.