Given that the Limbo stuff is in flashback rather than this whole mini being "how Juggernaut escaped Limbo," I'm not so sure it's going to be all that major to the overall story. Also, weren't you just saying this still could have been a solo story?
Regardless, Marvel wanted a solo Juggernaut mini, and maybe none of the other writers were eager to suddenly shove a solo Juggernaut story into their books. All I know is that Juggernaut getting a mini doesn't harm you or anyone else, and I'm happy to see Fabian Nicieza and Ron Garney getting more work.