No, they are related to the pool of people being diagnosed.

You're only getting a diagnosis if a) you have access to a psychiatrist and b) you are running into enough issues in your daily life to warrant having it looked into.

Life has gotten a lot more complex over the past few decades, so people run into issues more often - and earlier in life. Someone who would've just been "a bit of a weird guy" 50 years ago is getting an autism diagnosis today, simply because these days they run into issues as a child and are being put in front of a psychiatrist.

Even 50 years ago they weren't just slightly odd people who were otherwise happy to exist in a simpler society. Those people ran into the same issues and turned to alcohol, drugs, and suicide. The only difference is that nobody understood why they were suffering.