Several factors.
One I don't think has been mentioned yet, is due to the advent of the Internet, more ND people are coupling up and reproducing. I include muggins here and my husband, both highly suspected to be on the spectrum
Our daughter is predom non verbal, autistic etc. She was full term BTW, 2 weeks overdue, even.
We're just better at diagnosing I think for the most part.
I can definitely reel off a laundry list of people who I went to school with in the 90s/00s, who would definitely be diagnosed if at school today, myself included.
I think rates of neurodivergency are still not fully recognised tbh.
We're, as a country, shoving children like my daughter into mainstream settings they cannot cope with which is why people are seeing more. Families like ours also now have access to social media so you'll see more of us socially that way, as We're no longer hidden away like a dirty little problem.
I wish all this awareness had been around in the 90s/00s. Might have saved me a lot of trauma, tbh. The body keeps the score. If you think your kid may be ND, get them assessed. Even if they seem to be coping well in adulthood, stress can quickly unravel them. Sorry but it's what happened to me.