[Causality1]

Do the detailed results of the study contain all the data for the participants interests?

And if Instagram personalized the newsfeed of each user according to their personal tastes, the diversity of posts in their newsfeeds should be skewed in a different way for each user

That seems like a wild underestimation of how much a group of 24 Instagram users choose to look at sexy pictures over other topics. "Instagram behaves as if people are thirty percent more interested in sex than any other topic" frankly seems low.

[Tade0]

It's probably somewhat lowered by the other provider of sexual imagery, namely porn.