Instagram suggested user

a quick question from someone who doesn't know much about Instagram
how does a user become a suggested user? is it a matter of number of followers or something else (because looks like its not the followers count)
does it has something to do with the amount of pictures, the quality, hashtags etc?

From my understanding a suggested user is unique to every single account based on what you follow, like and also what the people you're following also like.

I'm quite confused about this, too. I've come to believe that you get the 'drop-down of suggested users' only when Instagram truly identifies who you are and who relates most to you. I have over 18K on my personal account and I did not get assigned one yet. But a friend who works in Fashion PR got one. She is at 15K. My public niche account (108K) also has one. But again, I have noticed major accounts with over 1M followers without the drop-down button. Identity crisis, I suppose. Haha.

I have reason to believe that hashtags play a major role, too. I do not use any on my personal account, so it seems IG is having a hard time understanding who I am and what I do. But I do use them on my niche account and IG was able to suggest my biggest competitors. Sucks that they are getting followers via me. But honored to be in the same category with accounts that have over 2.3M followers.
If anyone has more on this, I'd like to hear.

right suggested user only what kind of follow based . . . .

I think the more quality photos you will share on instagram the more you get chances to become a suggested user.

I think it shows up pictures of my friend's friends. Sometimes I get popular pics with xxK likes. Sometimes they are just an ordinary pics with 2 likes.