they could've just done like Degrassi and kept some old cast members and brought in new ones the kids do go to a performing arts school

They would get rid of their best show...just when it was getting great.

That makes no sense for Victorious to end. None of the cast, and I mean none, has a large enough fanbase to be successful outside of Nickelodeon...just yet. And with iCarly ending, Victorious would've been the flagship show for Nickelodeon, but I guess they're placing all of their cards in the new Queen of Nick and that sidekick from iCarly.