How Jane Foster Becomes Thor
5. Thor Is No Longer Worthy
2014's Original Sin comic book arc largely revolves around Nick Fury and the Avengers investigating the mysterious death of Uatu the Watcher.
In Original Sin #7, Fury whispers something into Thor's ear. We don't know what it is, we don't know how it does it, but these choice mumblings cause the God of Thunder to no longer be worthy of lifting Mjolnir. It would take over two years for readers to finally find out what exactly was said to Thor, and even to this day there's a debate about whether or not this drawn-out plot point was just a big waste of time.
To cut to the chase, the three words muttered to Thor by Fury were "Gorr was right."
Who is Gorr and what was he right about, you ask? Why, let's break it down.
Gorr was the main villain of so much of Jason Aaron and Esad Ribici's God of Thunder run. On a mission to lay waste to all of the gods across the universe, Gorr inevitably ends up butting heads with Thor. For Gorr, he sees the gods as arrogant, selfish, petty beings who are doomed to do more harm than good to the universe.
It was Fury's assertion that "Gorr was right" which made Thor realise that maybe Gorr had a point, which caused Thor to question his own place in the world and whether or not he really was worthy enough to wield the power that he was given.
But with Thor now not worthy to lift Mjolnir, that created an opening for somebody else to step up to the plate...