On the one hand, it's because some people want to feel 'special' about having autism, so they pick a bunch of talented, popular people and claim that they have autism too.
"These special people have autism! I have autism too! I'm also special!"
On the other hand, some people want to say bad things about autistics, so they pick a bunch of unpopular criminal types and claim that they all have autism.
"These losers have autism. You have autism too. You're also a loser!"
On the gripping hand, the people making these lists are probably not qualified to diagnose anyone - especially those they've never personally known - and may even be self-diagnosed poseurs themselves.
So when you see a list of "Famous People With Autism", check out the credentials of those who compiled the list. Chances are that no appropriately-trained and licensed mental-health professional would ever 'diagnose' someone without at least one personal interview.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.