Until Avatar and sorta/kinda later TMNT Nickelodeon has *never* attempted to making anything but comedy cartoons.
They aired a handful of adventurous shows and fairy tale anime programs in the early nineties as well as a few reruns of cartoons that were both humorous and adventurous but Nicktoons as a brand then took off and they didn't look back.
Spongebob made them all the money just as the Rugrats were wearing thin and with Avatar and (again, sorta) TMNT as the big exceptions they measured a show's value by if it could or could not measure up to Spongebob. But even Avatar was treated like shit by the network and shunted over to a different channel as soon as possible.
Anything else in terms of cartoons has basically been given brief exposure and packed up. They aren't trying to make blocks of cartoons anymore, not trying to come up with several hits, they just keep trying to bank on hitting a huge grandslam out of the park and drop anything that doesn't do that for them.
