The video you linked would be stupid easy to reproduce by recording a voice over after scrolling ads on Facebook for a minute. If you want to convince me, you would need to perform a controlled experiment with multiple unrelated search terms, fresh Facebook accounts with no browsing history, etc.

Or, what if this is real? Maybe the YouTuber wasn’t just phishing for view counts with clickbait to boost his channel and actually did make that video in good faith and sure enough, Bluetooth speakers show up in his feed? What’s to say he hasn’t been seeing Bluetooth speaker ads because he’s a tech inclined, middle aged man with disposable income and the opposite effect is true: maybe he subconsciously chose Bluetooth speakers because he’s been seeing ads for them on Facebook recently? Our minds aren’t exactly good at keeping track of that kind of thing and advertisers take advantage of that shit all the time. Look at the familiarity principle or mere exposure effect.

My point isn’t to say Facebook and Google don’t collect tons of data about us, they do that all the time for sure. It’s just that there are simpler, more reliable and less processor intensive ways to build a behavioral model. Google knows where I work, what I search for, how old I am, how many kids I have, what YouTube videos I watch, … There’s more than enough there to figure out what kind of ads to serve me.