I'd suggest reading Michael Hudson's Superimperialism for some background on why the US went off the gold standard. To succinctly summarize, it's because the US had dug itself into a massive balance of payments problem in the post-war period, primarily due to the imperialist wars in Korea and Vietnam, and had no way out beyond simply telling the rest of the world that it wouldn't be bothering to balance its payments anymore.

Dropping the gold standard was a means to an end, not an end unto itself. It also wasn't done overnight in 1972, there was more than a decade of soft-dropping leading up to the final event.

I always cringe a little internally when I see someone pointing at the dropping of the gold standard as The Thing[TM] which has defined the neoliberal era, as in my experience it's some sovereign citizen type dreaming up some anarcho-capitalist world in which gold (coin) and lead (bullets) are the only two payment instruments worth anything and there is no such thing as society anymore.