Does anyone know how the explore page works on instagram?

[Jellybellyqueen]

My DC wanted to set up an instagram account to follow you tubers and various funny/cute accounts, so I went on mine and h's accounts to see if DC was likely to innocently come across anything inappropriate.
I follow lots of arts/crafts/food accounts, and don't actually use it very often. My 'explore' page was full of that kind of thing. Nothing inappropriate. The only time I did have a scantily clad woman on a bed pic on there was just after h had started an account, while working away. Didn't think much of it at the time, and as I said, I don't use it that often.
H has used it a bit while away, judging by his posts but says he rarely looks at it now. When I went on his 'explore' page, there were quite a few pretty lady type pics, and when clicked on, underneath the pic in the details, it says 'based on people you follow'. And some even more explicit accounts are suggested after this. Looking in his 'following' and 'followers' list I didn't see any odd accounts, it's mainly work friends and organisations. But I do remember So, what does that mean?
Either:

1. He followed some dodgy lady accounts while away and since deleted them, but that still affects his suggestions?

Or:

1. Someone he follows looks at and follows dodgy accounts, which are then suggested to him?

Or:

1. Something else?

I dunno. Anyone else know anything?

You can like pictures without following the account which the algorithm would use to show you more of the same in the explore function.

Thanks sit. Nothing showed up in the likes list. I doubt he'd like anything like that anyway, in case I somehow came across it!