The article you linked does not support your statement
The "scandal" wasn't that GM conspired to put streetcars out of business, but that they conspired to monopolize interstate commerce. That's what they were convicted of. They wanted to make more money, and they bought streetcar lines and replaced them with more economical buses, which they happened to build. GM built (and builds) locomotives, too, so had electric trolleys been more economical, they might very well have monopolized that market rather than converting to bus systems.