It's an interesting time window you chose. Why would there be an anomaly during that window (if there is one)?

Perhaps it is due to the outward-facing, civic-oriented values coming out of WW2?

There was a lot of reflection in America on what went wrong in German pre-war thinking and culture coming out of that period.

The WW2 men in their 20s in 1940 were in their 40s in 1960s and their political power would have kept growing through peer older politicians into the 90s.