[weichi]

AFAIK, evidence is pretty clear that delaying marriage (up to a point!) reduces the likelihood of getting divorced.

https://ifstudies.org/blog/want-to-avoid-divorce-wait-to-get...

Of course you are correct that lowered social stigma associated with divorce is also important. This topic must be difficult to study over very long periods of time, because so many things are going on (changing age of first marriage, reduced social stigma associated with divorce, women's liberation, changing religiousity, etc. etc.).