I would consider keeping Hook on the show to be jumping the shark, a failed jump. I would also consider them doing Frozen to be jumping the shark as well. Both of these things were changes that were made at the last minute because they thought it would keep people watching.
You’re thinking of a ratings stunt. Quoting the linked article:
A poorly-executed Ratings Stunt may cause a show to Jump the Shark, while having many in a single season may indicate the show already has.
Jumping the shark is merely defined by TVTropes as:
The point where a series is officially undergoing Seasonal Rot.
It is not something that is intentionally done, unless the writers are deliberately trying to screw over their show, so it will get cancelled. Whether or not Adam and Eddy are doing that is something we could debate for ages. I, personally, think they’re just that bad of writers.