Well, in a recent interview with Polygon, Microsoft Studios general manager Shannon Loftis tried to explain the delay and admitted Microsoft revealed the game way too early:
"I think we probably announced Crackdown 3 too early. We definitely underestimated the challenge of making sure the quality bar of all three [of the game's] modes was high and it delivers on what we need to deliver on. So, we had to take the extra time, [and] make sure that we're delivering the game the Crackdown fans want. It was a super hard decision to do that, and it was made harder because we announced the game [early].
In the past, we have made the mistake of announcing some exclusives a little bit too early. We're trying to learn from that mistake and do better, so we have a [few] that are in development now that we're not talking about. We're in this for the long haul, and we wanna make sure that not just in the spring of 2018, but in the summer, and in the fall, and the spring of 2019 that we'll have great, unique, fun experiences for Xbox gamers."
Recently, there's been a general move away from announcing games early, as it leads to problems exactly like this. Sony has also said they'd rather keep quiet about upcoming games, and, of course, secretive Nintendo has been doing it for years. Having to wait longer for games to be revealed may sound like a bad deal, but hey, you can't miss what you don't even know about, right?
Crackdown 3 rocket jumps onto the PC and Xbox One in spring of 2018.