Because autism is usually paired with socio-emotional developement deficiency, when someone is suffering from such condition, the person's emotional responses to social stimulation are similar to a child's. Because of this, they get emotionally overwhelmed easily. They are usually under sensory overload, which is, together with the emotional overload , leading to discomfort, hysteria, panic attacks and all sorts of nasty shit, understandably they want to avoid this at all cost so they are mosty drawn towards activities, patterns and people helping them to avoid an emotional overload. Just like, as you probably guessed, being treated like a child by someone you trust, being protected from enviromental hazards just like a little child being protected by it's parent. The rest is just emotional memory, people tend to connect certain emotions to early memories, like how someone felt much more comfortable after being changed, being fed etc.
I can't say for sure that autism is related to this fetish, they just happened to have a similar attraction targeting mechanism.