Considering that life expectancy for a 30 year old man is around 79.3 in Germany 2018, and you're reading it to be 76.9 in 1930, that's far less change than I have ever heard anyone previously suggest.
First, 2.4 years on average is significant. Second, the scholarly average is for people who were on average 54 when appointed to their position. That means there is no childhood mortality or deaths below that age to bring the average down.