I believe the welfare state destroyed marriage. It used to be that a strong family was needed to survive and succeed in the world. Now the family is an impediment to success ... and you just vote for free sh!t when life gets tough.
The left understands how to change incentives in order to change society.
Conservatives are often left defending something when the battle has moved on.
If you want something less of something than tax it is an example of an incentive changing behavior.
With marriage the incentives have change so that it is a bad deal for many men. Thus they don’t want to get married.
Change the incentives and you will change the outcome.