Why did they make episode 65 of Teen Titans?

Yes, I'm 21 and I still watch Teen Titans. It was an awesome show. So I know this show has been dead for years now, but I've been re-watching the episodes (again) and I still can't figure out why they ever made episode 65. It just makes no sense since they add so many new elements with Terra suddenly showing up again, this new seemingly unbeatable creature, and Slade comes back, sort of, and then it just ended! I've heard people say that they stopped it because they didn't have the money or the ratings were down, but from what I've seen, Teen Titans was incredibly popular when it ended and it wasn't a money issue. So why did they make ep. 65 and then just end it instead of leaving it at 64?