It's the other way around, autistics are inherently easier to manipulate, primarily because they don't readily understand deception. Autistics tend to be truthful, even when it may come as a detriment to themselves and when they try to lie they generally can't ever tell the same lie twice. Likewise they have a big problem discerning the credibility and intentions of others, mostly due to their general inability to read other people's emotions through facial expressions, vocal intonation, vocal inflection, eye movement, mannerisms, etc, etc.
As a result autistics are very easy to manipulate and control and the more autistic a person is, the easier it is. Chris Chan obviously being the most notable example. As someone with severe autism he's been tricked and manipulated so much it's no longer even all that amusing.
The other thing is branding, autistics tend to gravitate towards childish depictions, over simplifications, colorful characters and so forth. So if you take a fun cartoon frog like Pepe and you start rebranding it with neo Nazi themes it doesn't take much to build up an audience of autistics who will suddenly buy into a bunch of bullshit. Of course it also works on the opposite end of the political spectrum as well, especially with current mainstream media like Steven Universe and My Little Pony.