Why did definition of autism change from the one maybe 40 years ago?

AUTISM. This neurodevelopmental disorder has attracted a lot of research and emphasis on how to improve cognitive and behavior disorder. Intensive early multidisciplinary approaches are done at home and in school. Treatments are given to control mood and behavior. Overall, there's a lot of improvements than before.
Schools/research/$$$. In the late 70's burdens were put on schools receiving federal dollars to educate kids in the least restrictive environment.Efforts to classify and help define treatment options increased. The "autism spectrum" disorder was created lumping many special needs kids into a category that generated better funding for programs. True autism is really the same, but lots of others are put in the same tent.