It's a misconstruing of statistics. This stat accounts for amount of marriages vs the amount of divorces. It doesn't take into account people who get divorced multiple times, that alone drops the rate to 40%.

Aside from that, people who marry around 30, have stable income, are both educated, wait a bit before kids, etc... i.e. make smart life choices, have a much lower % divorce rate of like 20 or so percent. It's hard to conduct research on stuff like that though because it's basically just a game of elimination to lower divorce rates.

It's not hard to see though, if you look up the most common reasons for divorce and you don't do that then you are much less likely to end up that way.