If you compare it with Gold
Which you shouldn't do because gold is a very volatile commodity. It went down from 2012 to 2018, then up from 2018 to 2024, then it went up extremely quickly since 2024. Gold is just something people put money in based on FOMO, or based on fears of stock market crashes, or based on other "vibes".
In addition, a lot of the world's gold is simply held in the form of jewelry in India. It's not even used as a direct "investment", it's just a pretty, shiny metal.
the USD moved in lockstep until the US left the Gold [Standard]
You'll never guess why that happened... although if you look at the name of the standard, it might give you a clue.
which is why a single blue collar salary that used to be enough for a good house, a car and the expenses for a family of 5 in the 60s
In the US. You know, essentially the only industrialized country that escaped from WWII with its manufacturing infrastructure intact, and was, as a result, supplying the entire world while everyone else was rebuilding.
The UK was another victor in WWII along with the US, but their workers weren't living in luxury. Rationing of meat ended in 1954 in the UK, nearly 10 years after the war. If you want to know what it was like in the UK in the post-war period, just look at stories of the early lives of the members of the Beatles.
In the US, the post war period not only followed the war, but also the great depression. The great depression ended with the New Deal, which shifted a lot of power from the rich to the workers. Workers from 1945 to the 1970s or so greatly benefited from those policies.
So, this 1960s family with 5 kids, a car and a good house on a worker's salary wasn't typical. It was probably the best off that workers were in the world since European workers who survived the black plague -- and all it took was a devastating world war that destroyed the infrastructure of most of the world's developed countries, other than the USA, plus a devastating depression lasting a decade that forced the government to institute programs that gave workers benefits.
(Oh yeah, and it only applied to white Americans.)