Amazed that the site does not call out Nixon completely abandoning the gold standard in 1971. Financial investments thusly did not need to be backed by actual assets anymore, to the point of today where the whole of money is loans against loans against loans.
That theory would explain financial gains going up faster (eg the pie getting bigger, more return to capital), but not a stall in wages for workers. Worker productivity went up, but wages for workers did not. ~1970 is about when the % of workers in unions really started to fall in the US.
Proof: look at stock returns when management pays more wages vs cuts wages/jobs