As someone who lived through this time period (albeit as a child), there was a phase transition in the way mainstream America treated government regulation around this time. It was much more common for politicians of both parties to advocate micromanaged regulation before this; hell, Nixon imposed price controls on private business to fight inflation. https://en.m.wikipedia.org/wiki/Nixon_shock#:~:text=Nixon%20....

Rand's work wasn't held in high regard... or any regard at all, really, until after her death in the 80's.

I don't disagree with the general sentiment though.

The idea of opposing excessive regulation isn't the same thing as this idea that regulation is a sliding scale with "more = worse" and "less = better". But yes, opposition to regulations did exist before. The former isn't a Koch thing, the latter is.

Atlas Shrugged was more the manifestation of the wet dreams of snowflake industrialists who felt intimidated by union power and communism (which were significant in the 50s, hence the rise of the middle class).