Since you're posting on Hacker News you're probably in a pretty high income bracket, and your married male friends probably are as well. High income brackets have seen pretty steady marriage rates, and as someone also in this bubble, they tend also to have men with more egalitarian views on marriage. But the flipside is that high-earners tend to delay childbirth-- they have to, because you need a lengthy period of education and work experience to get to that high bracket.
It's lower income brackets where marriage rates are really collapsing. A lot of this is economic-- the earnings potential for lower-class men has eroded-- but it's also the men in these income brackets tend not to have adopted upper-class views on egalitarian partnerships, and their potential partners aren't having it.
So among high earners you have stable marriages but where they can't start having children until their careers are secure, while among low-earners the men are both economically and temperamentally unacceptable to their partners. So fertility collapses in both groups.
If this view of marriage sounds unfamiliar, you might want to see e.g. [0], in particular the point about how "top-half marriage and bottom-half marriage are so unalike they might as well be completely different institutions."
[0]: https://cathyreisenwitz.substack.com/p/marriage-is-down-beca...