My money would be on coincidence. How often did you buy something and got irrelevant ads? I had such a coincidence happen to me once. I saw an ad for a product

My money would be on coincidence. How often did you buy something and got irrelevant ads? I had such a coincidence happen to me once. I saw an ad for a product I've never heard about online... and a short while later, I saw the same ad on non-smart broadcast TV, billboard, in print or some similar place where I could be sure that the ad was not targeted. Had it happened the other way around, I would have doubted it myself, but it was clear that this could not have been anything but coincidence. Besides that, why would the company behind it spend money on promoting the very product that you already bought? If anything, the fact that you bought it would be used to not show you ads, at least until some time later when you'd be likely to buy another one. (Retargeting frequently gets this wrong because they see the interest but don't get the purchase information.)