Nick did not want to put production of Spongebob on hiatus. It was the choice of the show's creator to not make any more new episodes and to concentrate on the movie's production. From a creative standpoint, I'd rather have Hillenburg laboring over the movie than spreading himself thin between new episodes and the movie. All of his creative energy goes into the movie that way. Nick has to space out the airing of the remaining episodes in order to maintain a high degree of interest in the show until the movie. If Nick had their way, they would be running Spongebob episodes all day long with new episodes airing frequently. Nick really wants to continue production of Spongebob after the movie, but that isn't a certain course of action as we all know.
Nick Jr is a brillant idea. Smartest thing Nick has done in a long time. Dora is the number one preschool show. Nick is taking away the market that used to be dominated by Elmo. They have even made Disney start to swarm in their pants. Spongebob is the new Mickey Mouse--brand recognition-wise. From a business standpoint, Nick owns the children's market and has even made a big dent in the adult market with their cartoons. Just because you are too old for Nick Jr and the shows don't appeal to you does not make it dumb. Nick is a company and therefore has to make money. If Nick got rid of Nick Jr., they might as well go out of business.
Of the choices above, the worst decision is cancelling Invader Zim. I think Nick doesn't know who to properly maintain shows that aren't as comfy kiddie-fit as Fairly Odd Parents or Rugrats. Invader Zim might have flourished had it been a Cartoon Network property. To me, that cartoon didn't mesh well with Nick to begin with. So I guess the worst decision they made was buying a property like Invader Zim when they didn't really know how to market it.