- The 2010s represented a progressivist left-ward shift in America and the excesses of that movement are provoking a reactionary conservative shift in the populace in the 2020s: https://www.noahpinion.blog/p/seven-reasons-america-is-heade.... This is cyclical is the same thing happened from 1960s to 1970s.
- The concept of population collapse entered mainstream discourse in the early 2020s and is now being accepted as the major concern for humanity moving forward, a 180-degree turn from the previous concern of overpopulation. This is something unprecedented in human history as no human has ever existed in an economy or society where the population was decreasing so all the "rules" we know about life are suddenly subject to change unless birth patterns change significantly.
It’s a product of the rise in white nationalist/supremacist movements and white replacement theory. Pro-natalism with the explicitly racial content omitted (though even their often tied to overt appeals to eugenics and/or framing it as intra-societal/cultural competition, which is itself only a shade different from racial/ethnic competition, but for some reason doesn’t produce nearly as strong a negative reaction) is a face that can be shown to audiences that aren’t ready for the full-strength message.
I’m not saying every vocal pro-natalist is a white supremacist (most of the high profile ones are, though), but that the rise in white supremacy and the prominence of white replacement theory within the rising white supremacy is a big part of the explanation of why pro-natalism is a lot more prominent right now than in the recent past.
There are probably other related factors too, like increased awareness of population decline, but I think both reasons are intertwined.
Also there is a biological urge, so it's probably not that much of an uphill battle. Though unfortunately people also contend with biological clocks and realize that they want kids when it's already too late. I feel very bad for those people, and so if you can re-normalize the idea of starting a family, then maybe you can reach those sorts of people while they still have time.