[tempest_]

Generally they optimize for engagement not informing you of your friends activities.

So it had likely pigeon holed you into a class (age, sex, relationship status, whatever sites the facebook button has said you were on) and it is showing you things that "similar" people have engaged with and lets be honest a good amount of the popular posts on social media are thirst traps...

I know you can download the information from Facebook about the profile it keeps on you but I am not sure you can do the same for Instagram. Regardless it was pretty interesting seeing what it had in there. For me some of it was correct and some was wildly off.