After four very well received new episodes that has dived deep into the lore, Star Wars Rebels is going back on hiatus for four weeks. The next scheduled episode of the new Mandalorian themed story won't air until February 18th, squarely in sweeps. Which might explain the move. No specific reason was given.
This isn't the only show doing the staggered season approach. Lucifer, Gotham and Brooklynn Nine-Nine are doing a couple episodes in January and then going on hiatus until spring.
Most shows have taken up the practice in the last few years of doing a mid-season break shortly after Thanksgiving and coming back in late January. But to take a second break after only three or four episodes is something new this season. Will fans be okay with new episodes in short bursts like that? Or will they lose interest by the time the shows return again? With Star Wars Rebels its only four weeks. But for Gotham it will be just shy of three months (Episode 14 airs January 30th, episode 15 airs April 24th). And in the case of the Fox series, it takes them out of February sweeps… a crucial time for getting new advertisers and getting renewals. Sweeps happens in November, February, May and July. The first two are the biggest in that they take place during the regular network television season while May does as well, it also contains the Up Fronts where networks announce their renewals and fall schedules.
The Disney move on Star Wars Rebels seems like it's trying to position the series to be hitting big episodes during February sweeps. It's really hard to tell what Fox is doing.