Yeah why would ANYONE do such a thing?
One is a sequel to a critically acclaimed and almost universally loved game, that people had been hoping for a sequel to for years, but didn't know if it was ever coming.
The other is the sequel to a critically slammed game, that many people hated and represented a developers fall from grace, and everyone knew was in development.
Look, Destiny 2 is obviously gonna be a hit no matter what, Destiny 1 proof of that. But I imagine that Bungie wants to try and win back the people that were dissapointed with Destiny 1 and also show that they can still make world class games. I don't think announcing the game with zero information is the way to do that.
I think the response has shown that's not true. 1200+ post thread on GAF, trending on Twitter and Facebook, a lot of fan speculation just over the artwork alone.
This is good marketing. Give people something small, let them discuss it and want more, then give them more information in a day or so.
I think it's a great way to get the fans of Destiny 1 excited. But beyond that I don't really think many will be excited, I could be wrong of course.
But as someone who bought Destiny 1 and TTK. I really need to see something that tells me that Destiny 2 is bungie's return to form before I get even a little bit excited