If you found the post interesting from a “how scams work” or “digital awareness” angle, that’s definitely a valid discussion. But if it was presented as a real tool, it’s fake.
Any website, app, or browser extension promising “Facebook profile viewer online” is almost certainly a scam — they often try to steal login credentials, spread malware, or collect personal data for spam. facebook profile viewer online
It sounds like you came across a post claiming there’s a way to see who viewed your Facebook profile. Just so you’re aware: that lets you see who viewed your profile. If you found the post interesting from a