Clinton, Bush, and Trump were all born within a year of when Japan's surrender ended WWII. Fittingly, the impulsive Trump was born a mere 9.5 months after.
Obama gets lumped in with that generation by demographers but was born 16 years after WWII ended. Less boom than echo.
Clinton, Bush and Trump time traveled together, hitting all the major events at the same age.
It is not just that the 2020 candidates include what could be the first Jew, black, woman, black woman, or gay to be president. It also includes members of the silent generation, baby boomers, gen x, and a millennial. These candidates have hit major events at very different stages of life and would bring a very different perspective to them. Bernie Sanders was 4 when Japan surrendered and the horrors of World War II would have been relayed to him as fresh stories by family members when he was a little boy rather than as distant history as it would have been for Pete Buttigieg who will be younger when he's sworn in than Sanders was when Buttigieg was born.
Here is a way to think about the age of the candidates in terms of where they were when historic events happened. (And obviously for the candidates, the age when "sworn into office" assumes that they would actually win the 2020 election.)
Oh, and yes. I know that Ocasio-Cortez is too young but I thought it was interesting to put her there for comparison. And she's too young for 2020 but she'll be old enough by 4 months to run in 2024.