[cynest]

I would be willing to bet that the increase in general acceptability of divorce is the main factor.

[roel_v]

'the main' I wouldn't say. As women become increasingly economically independent, they open up the practical ability to get a divorce. Many women used to have to stay even in abusive relationships just because they had no other options. Women who can provide for themselves have the option to leave a relationship when they find it no longer in line with their life goals or desires.

[Tichy]

Could it be more acceptable because women on their own, as well as men on their own, are better able to survive these days?

I think frozen meals and washing machines helped the cause of feminism a great deal...