All along, the Mainland Plane had faced a grave problem in its war against the Devil Race.
They had no way to strike at the Devil Race's roots.
The battlefields were all on the Mainland Plane's side. Whether the continental allied forces won or lost, it was this plane's land that suffered destruction. They had no means of damaging the Devil Race's native planes.
Yet striking their native planes was a necessary step to defeating the Devil Race.
Otherwise, whenever they failed in another plane, they could simply retreat to their home plane, slowly rebuild, replenish their losses, and march out to war again.
As for why they could not attack the Devil Race's native planes, it was not because interplanar passages were disrupted by storms. Rather, the gods of the Devil Race—at least the gods of Hell and the gods of the Abyss—were relatively united. They had chosen to seal off their planes, turning them into one-way valves. From Hell and the Abyss, passages could be opened to other planes, but from other planes, one could not set a passage's destination within those two planes.
This directly caused Hell and the Abyss, which had once been reachable, to become inaccessible.
The Mainland Plane now possessed an ultimate solution capable of killing tens of thousands of Devil Race members at once, yet had no way to apply that solution to the Devil Race's home planes.
They had "nuclear bombs," but no "carrier rockets." They could not throw them at the target.
It was unclear whether Hell and the Abyss could accomplish this while the Mainland Plane could not because some technical hurdle had yet to be overcome, or because the gods here had never reached a unified consensus and thus could not join forces to seal off the Mainland Plane