Sure, the automotive industry stood to benefit from the decline of rail travel in the US. But they didn’t really need to do anything for that to happen on its own. Reality is far less interesting than that. Turns out when you have tons of fertile land, even pre-industrialization your population tends to spread out a bit (the vast majority of Americans used to be farmers). Today the US has 3-5X less population density than any country with high speed rail. Autos saw massive success in the US due to this fact, and their prevalence reduced the demand for rail travel as a side effect, it wasn’t some top down evil conspiracy.
It’s fun to blame everything on evil big business or evil big government, but it’s also important to look at the first principles and base properties of the issue at hand first.