Can anyone with knowledge on Instagram help explain what's going on?

One of my memes got removed which was odd because I only let people I know follow me. I removed all of my followers and am shutting it down once I get my data emailed to me because I don't use it much anymore. It still said I had 1 follower even though no one showed up. After waiting a few hours and refreshing every once in awhile the follower finally showed up and I removed it. I assumed it was someone who had reactivated their account after a very long time, saw my post, didn't like it, and reported it. It said I had 0 followers. A day later, I now have 1 follower who won't show up again despite not accepting any requests or anything. What's going on? Glitch? Hacker? I know it isn't fool proof but I use two factor authentification and a strong password. I don't believe it's the same account that followed me last time because if I block it I still have 1 follower. I reported it to Instagram but that's about as good as if I told a wall what was going on.