Still a high chance for a coincidence.
How? Its an isolated environment where the conversation is being had.
And the human mind tends to see patterns to structure the world.
Its an explicit viewing of a commercial of a type that is not normally seen. Not exactly a pattern.
Shoe advertisement is not particularly rare in the web.
I never saw any on YouTube until the evening of that conversation. /shrug
Coincidence in the sense that the ad that you saw had absolutely no connection to your talk. It was just a random ad. No all advertisements are targeted precisely. I work in the field and a lot of campaigns on YouTube are just targeted to a selected YT-channel, or a topic like sport videos, or maybe an age group. That’s all. You see an ad because you watched a channel. Like on TV.
Coincidence in the sense that the ad that you saw had absolutely no connection to your talk. It was just a random ad.
I’m willing to admit that’s possible, but when I haven’t seen any for a couple of years (truly), and then see one the same evening, that seems like more than just a coincidence to me. /shrug