When Riker got promoted to captain, he actually considered Worf for the position of first officer, before he even considered Data.
As second officer, it would be assumed that Data would automatically get the first officer position since it's like he's a first officer in training.
Riker totally skips this idea and considers promoting others.
I believe the reason was since Data was already slated to become First Officer of the Enterprise under Picard, this was pretty much stated in Nemesis
Was this from Nemesis or the show?
I got this scene from Best of Both Worlds-- when Picard was kidnapped by the Borg and Riker was made captain by Admiral Hanson.
So it's funny because Data had been 2nd Officer for about 3 years at that point, it seemed it would have been natural to automatically promote Data to First Officer.
Instead Riker said he actually thought about Worf for the position- and then he said he seriously considered Data for the job
Ah. My mistake, I was talking about Nemesis
I think the real life answer is that it was early enough in the life of the show that positions weren't quite as cemented as later. In universe, I guess you could say that Riker simply thought Worf would have been a better fit for First Officer and promote him over Data. (Data wouldn't have objected, and Riker always seemed to get along with Worf much better, so it would have been a good working relationship)
Chain of commandwise, I suppose Worf would have been the Third Officer by this point anyways, so it really wasn't a huge jump.