“Why is Amazon trying to sell me an X? I just bought an X. Idiots ”

Firstly, if the tracking was good, amazon should know if an item was returned. It seems unlikely you'd keep a fridge you don't want and then buy another from the same supplier.

Secondly, and perhaps more indicative, they usually advertise the exact model you bought. They're clearly not doing it because they think they'll capture buyers remorse or the other reasons suggested here, they're doing it because the adverts are only using the information that you were browsing those items and not that you bought it.

You get the same adverts if you browse an item and then don't buy it. Yes, amazon wastes a lot of eyeballs on adverts for things that people won't buy.

There is another reason that isn't even explored in this article, that sometimes it's important to advertise things that people already own to make them feel better for having bought them.

However, the crude "here's a picture and link to the item you own" adverts aren't brand-alignment adverts, they're just bad adverts.

Perhaps it's actually an amazon brand-alignment. By reminding people of a recent purchase (that presumably went well) they elevate Amazon as a brand that delivers.