I think it’s because the stigma of having a “mental” illness has been reduced significantly since 1985. I see lots of anxiety related material in social media and websites geared towards teenagers and young adults. So kids are more educated about anxiety and less likely to feel embarrassed about admitting they have a problem with it.
I do think though, that with all the information available online about mental illness and that talking about it has become normalized, that there are many people who diagnose themselves and say “Oh, man - I get anxiety so bad”, when they’re just feeling normal emotions. There’s a difference between feeling anxious/stressed and having an anxiety disorder. Anxiety disorders are those serious enough to keep one from functioning normally in daily activities. I don’t think 41% of students at UCLA have anxiety disorders - they are just feeling normal situational anxiety.
See the table on this page that describes the difference. https://adaa.org/understanding-anxiety