On Facebook, it's a click of a button to block access to your friends list. My guess is, he just shut it off, which included you.. simply by default. Mine is still off and has been for years, so I'm not sure if the settings have changed with this.

I'll be honest, I don't like this guy, but I don't think he blocked your access to hide something. I don't think he put a lot of thought into anything and was just trying to make you "happy" by disconnecting himself from these followers.

Having said that, there's usually a reason why someone would follow someone. I don't really understand this feature if you're not on a friends list. What access do you get from clicking the follow button of someone you're not friends with? Was it just this one person (I can't remember)? I find it odd that a stranger would randomly do this by looking at a stranger's profile photo.