>IIRC, browser synchronization was a thing on Firefox well before it landed on chrome.

Yes, but it was bad. Chrome allowed you to sync just by typing your Google account credentials. Firefox relied on sharing a text file between computers. If you lost the file and reset your profile (as was common in old Firefox), you effectively lost all of your synced content. Adding a new computer was difficult and slow. Firefox ultimately failed the "could you explain this to your parents" test, and many users simply gave up trying to get it to work.