Los Angeles is the usual subject of this conspiracy theory,
that auto, tire, and oil companies bought up the trolley lines
to dismantle them, and make everyone dependent on cars. In
fact, a partnership of GM, Firestone, and Standard Oil ...

=v= Judging from the rest of your message, you're using the
phrase "conspiracy theory" to be dismissive. But in fact the
parties to this travesty were actually found guilty of ...
conspiracy!

... in spite of declining ridership and huge losses.

=v= Your narrative sidesteps the caue of declining ridership of
these streetcars. City Lines deliberately cut back service and
ran these things into the ground, so duh, of course there was
declining ridership. They replaced comfortable streetcars with
uncomfortable lurching busses (made by GM, using tires by
Firestone, and guzzling gas from Standard Oil).

But the final nail in the coffin was the citizens of Los
Angeles banging down the doors of City Hall, demanding the
trolleys be removed because they were blocking traffic.

=v= "The citizens of Los Angeles?" A representative sample,
a rent-a-mob, or a handful of dupes?

Ultimately it was the public who chose the automobile, all
by themselves.

=v= The public "chose" (and continues to "choose") what the
transportation infrastructure supports. Which is not by any
stretch of the imagination an "all by themselves" situation.
_Jym_