That's just because people died young. The mode (most common) age of death was over 75 in France for men in 1930. I'm not sure how WWII factors into that. It's now about 82, eyeballing it (yes, still higher).
People were not "old" and dying at appreciably higher rates given they reached age 60 back then. The general premise that there's a lot of rich old people now is true. But the factors that have raised life expectancy are probably working against this trend, and to minor effect, as they primarily raise the current number of kids.
https://www.cairn-int.info/article-E_POPU_1204_0683--the-mos...
People were not "old" and dying at appreciably higher rates given they reached age 60 back then. The general premise that there's a lot of rich old people now is true. But the factors that have raised life expectancy are probably working against this trend, and to minor effect, as they primarily raise the current number of kids.