Is it a case that back in the 80s nothing was known about Autism and a child who had traits was dismissed as been hyper and a bit of
a loner?
Partly. A multitude of factors really.
Mostly, what was known about Autism, and the portrayals of it, back then.
There was a view that all autistic people had severe needs, or were rain man type characters.
There is also something that threads through all challenges people have that don't present as severe or in line with general thought: People have a tendency to disbelieve someone who is struggling if it's with something they don't struggle with themselves.
I speak to a lot of parents of teens diagnosed with ADHD, ASD etc who put things in place for support, and ironically these may be things the child wanted previously but they thought he/she was just being difficult. A great example is electronic devices.
Many people diagnosed in later years who would have been in school in 80/90s will say they were labelled as lazy, defiant, difficult etc.
A challenge for many is they may excel in one subject, say maths, and struggle in others, so the prevailing thought is they could do it if they wanted to say in English or History.