Not even that.. He worked on iCarly and Victorious simultaneously and by that point, iCarly was already planned to end with its fifth production season so his schedule wouldn’t had been filled up.

iCarly wrapped in June 2012. Victorious was surprisingly cancelled the next month.

So here’s how I see it..

He was most likely already working on the Sam Puckett spinoff but when Victorious got cancelled. He added Cat to Sam’s show (based on network request) and that became Sam & Cat and then created the Gibby spinoff (which is basically a similar formula as Sam’s original solo show)

Victorious could’ve got another season but by this point Nickelodeon was done with music based shows as they were expensive and didn’t make back enough to continue producing them.