It's probably that Lemmy isn't exactly mainstream (like Reddit), suggesting that people on Lemmy aren't normally oblivious to the ways of the internet. And most people on the fediverse are more adverse to the centralised mainstream social media companies.
Using Firefox would back up this assumption.

And that it has been widely known for a long time that Facebook tracks/collects/processes anything/everything it can get it's grubby hands on.

So, it reads - to me - along the lines of "how are you participating in the fediverse (suggesting some decent knowledge of internet/computer things) without knowing that Facebook is going to try and get everything (common knowledge) and that Firefox is going to try to prevent this (which is a prominent reason to use Firefox)"

OP seems surprised that Facebook is tracking them, yet found their way onto a fairly niche SM community full of people who care about privacy.

Someone clueless about Facebook data mining its users shouldn’t have made their way here in my opinion so I’m curious about the journey.