I've experienced this with a cat. I don't know what caused his trauma but I have never seen a cat more scared as him. And this isn't just shy or aloof, or don't trust human stray cat, he is like this dog in the video, just terrified of everything except his cat siblings.

It's taken my over 8 years of work to get him close to a normal cat. He is about 70% right now. Best I can do for him is give him safe places to hide, be quiet around him, and give him all the affection he wants when he builds up the courage to come to me for some.

Best thing is he loves to be pet but is scared of my towering over him so he figured out that if he comes up on my bed at night he can get lots of pets in the dark where he doesn't have to be scared of seeing me.