Jeremy leaving

Okay I haven’t seen a post about this specifically but how on earth did it make sense to the writers to just make Jeremy disappear, and then have Bonnie leave him a message that she’s back from the other side - and Jeremy said himself that he’s coming back as soon as Bonnie is back? Plus what was he actually doing? I can’t remember now but Alaric didn’t send him to college but some random bus at night to no idea where lol. I just thought about this and its actually so silly that they left his character like this, especially that Nina left after season 6 so surely Jeremy could have a more developed story? Interested to hear others thoughts!