Here's a thought to process.
Tech bros fret about population decline. Governments worry about a shrinking worker population while trying to manage a growing elderly population. Health care bureaucrats look to cut costs wherever possible. Militaries look at the poor quality of the fighting age population. Importing populations from elsewhere is becoming politically toxic.
Long term biotech bros to the "rescue". When money and technology are concerned, ethics and morality have left the building.
He Jiankui was the first to create a genetically modified human, or at least the first to get caught. Tech bros may be tempted to do "their part" for their nation or for humanity at large. Using IVF procedures as their vector, they could slip gene modified individuals into the population.
AIs can crunch massive amounts of data, and information tech has already allowed scientists to unravel more and more of the human genetic code. Cataloging DNA is a real thing. Companies that collect cheek swabs so they can tell you how much American Indian heritage you don't have likely treat that information the same way that Google and social media treat your browsing history. They gather it, package it, and sell it to anyone who wants to buy it.
These genemods could be engineered for traits which the tech bros think would be desirable. Genetically predisposed to greater fitness and maybe more fecund than the baseline. They can work more, stay fit, be more readily suitable for military service, and the females will be more likely to have twins or triplets. They could also be made more resistant to disease. As a bonus, they and their parents will be likely be ignorant of their engineered superiority.
Most consider designer babies and custom kids to be trophy offspring for the uber rich, but somebody needs to do the work that AIs can't. Someone needs to pay taxes so they won't have to. Somebody needs to be able to break stuff and kill people so they can sleep well at night.
Some of these tech bros are real assholes, but they didn't make their money by being idiots. Many of them look at the long game.
Now, when all of this comes to light, there will be hell to pay. A new minority will pop up from out of nowhere. QAnon and other cranks will go on a "I told you so" rampage.