I guess Bill Willingham thought his series was getting too dark
As the main Fables storyline is building up to a new baddie with the Empire's fall, the Dark Man has taken root (pun DEFINITELY intended if you get it...) we, the readers, are suddenly sidelined with a Jack story. Why this even needed to be a Fables instead of just a Jack of Fables story, I can't imagine. Bigby & Snow *could* have guested without the stupid storyline of Jack trying to take over Fabletown and the animal fables and corrupting the cubs...
And I don't see what this will have to do with the resolution of the Dark Man in New York/Baba Yaga in the Business Office. While I love Fables and adore the work of Bill Willingham ever since his Elementals days, this one could have been just NOT DONE and the resolution to the mystery of Kevin Thorne was lackluster and disappointing.