I see a mix across that generation as well. It seems some of those that struggle kept the mentality that helped their parents flourish: an expectation that you find a stable job and work it for 40 years. They weren’t exactly in the mindset to constantly hustle and constantly learn new skills. When globalization started to pull the rug out from under them in the 1980s many had difficulty remaining relevant in the economy.
However, every last one of their 5 siblings is indeed a millionaire after leading relatively modest middle-middle class lifestyles. Maybe one of them you could call upper-middle, but even they traded thriftiness in most areas for the appearance of wealth in others.