Wrong. In Detroit's case, street cars simply became uncompetitive with alternatives in transportation. The Detroit streetcar system was privately owned, not government run, and wasn't going to operate at a perpetual loss like modern government run public transit does. One of the biggest killers was as the city grew and changed over time, streetcar systems were fixed and inflexible so they couldn't quickly and cost effectively change with them. Detroit switched to a publicly owned streetcar system in 1922, and that too did in the system due to the inefficiency of government.
This was a common failing of these systems and often the cause of their demise.
Yes, in LA General Motors and Firestone colluded to get rid of the "Big Red" streetcar system and replace it with busses, but even if the streetcar system had remained, it would have operated at increasingly large losses as the LA region grew.
In the US, unlike say, Europe, most cities grew to become automobile-centric rather than walkable / public transit friendly. In Asia, land area is often limited and kept cities walkable and public transit friendly. In Europe, most cities were pre-automobile so they remained walkable and public transit friendly.
Today in the US we have a movement on the Left to try and reshape US cities into walkable and public transit friendly, but that horse has left the barn. It isn't going to happen, and that's why US public transit is so expensive and shitty--It simply doesn't serve a spread out car-centric city and never can.