Ask HN: How Does YouTube Pick Up Facebook Content to Show Targeted Ads?

Just wondering if anyone is in the know? I have a pretty 'refined' YouTube feed so anything unusual I will pick up very quickly. As it happens, I posted something on my FB news feed earlier today and a few hours later I was getting video recommendations on YouTube for that one thing. It's not something I have looked into or researched for the last couple of months, so it's pretty obvious that there are shenanigans happening. Anyone who has figured this out; mind sharing your thoughts?