I think it's due to the stigma on mental health going away. Now days people are more open to understanding their mental health, as well as understanding whatever conditions they have. So those saying they are neurodivergent tend to be people who don't fall in line with traditional norms. These could include people with autism, asperges, or something like severe anxiety, or even depression.
Awareness about our mental health is a big one too. Back in the past people were scared to say they are going through something. Now days we get mental health days out of work and have resources in schools to help those kids who may be neurodivergent.