Why did my new instagram account automatically connect to the Facebook account that was logged in on my iPhone?

[Sez]

I wanted to create a new instagram account unrelated and unlinked to my personal instagram and Facebook accounts.... so I created a new instagram on my iPhone using an email address only (a different email than what I usually use). I provided no FB details. However after a while I noticed that my usual Facebook friends started following me which means the new instagram account automatically linked to the Facebook account that was logged in on my iPhone. This seems really wrong and annoying as I wanted the new instagram to be anonymous. Hope that made sense. What happened here? What if someone else had used my phone to log into their Facebook and their account happened to be open when I joined instagram?

[Daniel]

Just Because Some Of your Facebook Friends Followed you on your New Account Does Not Mean Your Facebook Account Is Connected to Instagram its Not Possible for it To Connect to your Facebook Account Unless you Actually Go and Link it to your Account its Not Going to Do it On its Own

[Angeleyes]

It's not possible for that to be connected to your facebook account unless you set it to be linked to your account.