I think most people thought season 2 was the end because it LOOKED like the end .. they also didn't see Book of Boba Fett and the Mando episodes when grogu came back. So when season 3 came along, they didn't think things would be good without Grogu.
For Andor, I think most didn't know how it connected to Rogue One... Or maybe they hadn't seen Rogue One. Or remembered who Cassian Andor was.
I'm just saying it's more complicated past "not many fans left". Get a new movie that pushes the universe forward, you'll see more interest again.
All I see, is you making excuses Lucasfilm/Disney. How is it that you know specifically the reason fans aren't watching is that they are ignorant.
It's bad story telling to put a major plot point on another show and expect fans to watch that other show. Grogu being back with Din Jarin on Bobba Fett show is bad story telling. You may like Bobba Fett show but not many did. There were many reasons why Mando S3 was bad, one big one was Din Jarin being almost a sidekick to Bo Katan on his own show.
If your reason for Andor failing in viewership was because not many people know about it being related to Rogue One, then isn't that another reason that SW fandom is not as popular? They've seen so many bad Star Wars stories that they thought Andor would be bad too would be more the reason.
The Star Wars fans are still there but they just chose not to watch bad Star Wars hence it's not as popular as before.