For reasons that elude me, the Inhumans were given a back-up feature in a handful of issues of THOR in 1967-68, and a few of them were reprinted behind Spider-Man reprints in 1981.
“The Reason Why” was reprinted from THOR #147, featuring part of the origin of the Inhumans. THE JACK KIRBY COLLECTOR #21 featured copies of all the pencils for this story, with Kirby’s margin notes, to demonstrate one of the prime examples where the final product ended up completely divergent from Kirby’s original intent, and explaining a few odd points of the artwork.
As published, the story features a Kree Sentry detecting some activity, finding the city of Attilan, where their leader has just become the first to get powers from the Terrigan Mist. The Sentry explains to the Inhumans the role of the Kree in their creation, and declares the experiment a success.
As Kirby wrote it, the Sentry and Attilan had been in contact all along, and the Sentry was warning them not to experiment with those powers, in defiance of the Kree, and declares the experiment a failure.
So the story we got isn’t the story we should have, and the original does make more sense in the larger context of the Inhumans story. Fortunately, the art wasn’t modified, and was wonderfully inked by Joe Sinnott, so that’s okay. I love that half-page panel of the Sentry among the animals, and the various views of Attilan.