Originally Posted by
H-E-D
Up until around 2015, Marvel Studios and Marvel Comics were controlled by the same person, Ike Perlmutter. He felt like Marvel shouldn't be in the business of publishing comics for characters that would be in other studios movies. That's why the Fantastic Four books were cancelled for a few years. The X-Men were too big a part of the line to cancel outright, so he decided they'd need to come up with a replacement first. The Inhumans fit the bill and they became his pet project. He was the one who got Inhumans on the movie schedule, and when Marvel Studios got moved out of his purview, it no longer had the support to move forward.
Now, to be clear, there's no indication that Ike issued a directive for the comics to writer a story about the Inhumans replacing the X-Men. He isn't an editor, a writer, he's probably never read a comic for the past decade, if ever. The directive was just to retool the Inhumans to function akin to the X-Men; a property that allowed people from all over the place to manifest powers of all different sorts, while having a unifying factor that provides an inherent impetus for those characters to come together.
This is why the Inhumans went from being a property about an secret, insular kingdom of an different species, to a publicly-known world-wide genetic minority
I'd be very, very surprised if Ike at any point gave them the directive to explicitly pit the Inhumans and mutants against each other. I doubt he really cared about what stories were written with them past the point of establishing the NuHumans. It isn't really an indictment of the pre-IvX Inhumans franchise to discuss the impetus for its retooling. That's just the story of how it happened. It also explains why the Inhumans no longer seem to be an editorial priority.