It's because you are the exact target demographic consumer for that product, and it's visible in your behavior patterns when using your apps combined with what they know about you (age, sex, location, demographics, etc.)
Much more likely an explicit retargeting ad network that doesn't realise they already bought it.
Retargeting has been a thing for like 15 plus years now. Visit website for knives, ad network tracking cookie notes that down, same ad network later serves you ads for the same knives. Or some convoluted data sharing network that has the same outcome these days.
It's not much more likely. People don't realize but demographic targeting works really well. When you are a certain age, certain gender, living in a certain area, with a few other inferred characteristics, you're very likely to be talking about, thinking about, and buying a small set of product types
I think the OP knows best what happened to them, so I will leave it up to them to decide. But to get targeted for a product you just looked feels like pretty standard retargetting.
I don't disagree with your point that demographics can be very good and sometimes uncanny, that aspect I agree with. It is just the timing that leads me to believe it is retargetting.
