When facing Thor, Fury whispered something into the God of Thunder's ear that not only shocked him but left him unworthy to lift his hammer. This event would serve as the catalyst for Jane Foster to claim the hammer, becoming the Mighty Thor, and for plenty of villains to rise in the aftermath.
He was rendered unworthy, because in his heart he believed what Fury said was true. In effect, Thor knew “how it feels to be mortal” and in his mind mortals are unworthy of Mjolnir and the powers of Thor. It's important to note here that Thor's unworthiness was of his own design.
Even more people don't know the hammer has a name. During Marvel Comics Original Sin story-line we saw Thor Odinson become unworthy to wield the hammer. During a fight, Nick Fury was able to utter a simple sentence in Thor's ear. Whatever was said to Thor caused him to be unworthy to wield Mjolnir.
Is Thor still worthy in Thor: Love and Thunder? It is pretty clear that Mjolnir chose Jane, not because Thor was unworthy, but because Thor's oath had instructed it do so. Sadly, the hammer cannot cure Jane's cancer, and can only transform and temporarily empower her.
Thor becomes worthy once again in War of the Realms No. 6.
The chemotherapy is attacking the cancerous cells but Mjolnir doesn't identify the cancer as an illness just as another part of her it needs to protect. Plus chemotherapy really does weaken Jane and make her sick so it's easy to see as an illness on it's own.
In a moment of wistful affection for his girlfriend, Thor asked his trusty hammer to always protect Jane, and in doing so unwittingly enchanted Mjolnir to do just that. Just like Thor's father Odin once enchanted the hammer to only be lifted by someone who is worthy, Thor cast a spell that let Jane use its powers.
Having been adopted by Thor, Gorr's daughter has seemingly become the new owner of the weapon forged to defeat Thanos in Avengers: Infinity War. In Thor: Love and Thunder's ending, Love carried it into battle alongside Thor, who was once again wielding Mjolnir.
In The Unworthy Thor #5, which released in comic shops today, the words Nick Fury said were finally revealed. "Gorr was right." Three simple words that undid the God of Thunder.
Gorr planted seeds of doubt in Thor's mind, forcing him to question whether gods truly are as noble and benevolent as they seem. Nick Fury seizes on that doubt in 2014's Original Sin, telling Thor "Gorr was right" and rendering the god of thunder so disillusioned that he's no longer able to lift Mjolnir.
In truth, Thor is affected by the "Warrior's Madness," a sickness of the mind that Asgardians are vulnerable to. This takes the form of a Dark Valkyrie, a woman that only Thor can see, and who spurs him towards evil and destructive actions.
Odin strips Thor of his power and casts him and Mjolnir to Earth. Crowds of humans gather in an effort to lift it, attracting the attention of S.H.I.E.L.D. Thor eventually finds Mjolnir but is unable to lift it until he later proves his worthiness by sacrificing his life against the Destroyer.
Of course we know that Thor Odinson was eventually deemed worthy enough to wield the hammer. That is, until the events of Original Sin where Nick Fury whispered something into his ear that caused the hammer to deem him unworthy and reject him. That's how Jane Foster came to be the hammer's current owner.
Within the MCU, they have established Thor as an immortal, making him an invaluable member of the Avengers and one of the most powerful beings to ever exist. As a result he can be killed in battle, but he will always return to his body one way or another.
Thor's depressive state lingers, even in his dreams, and is centered on Mjolnir, its power, and the required worthiness of its possession.
Originally there was no restriction placed on the hammer for who can use it but after Thor's reckless behavior, Odin Borson placed an enchantment on it. This spell read "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor." Only those deemed worthy to lift Mjolnir can.
While Thor's short temper has been well-documented, his determination is also a major weakness. Thor's determination is a weakness in that he keeps throwing himself at an adverse situation to the point of threatening his life.
In their attempts, Jane tells him, "She won't be alone," signaling the fact that Thor would take the girl under his wing. Finally, before she passes, she tells Thor to keep his heart open, bringing Jane and Thor's story to a heartbreaking close.
But when he reaches that cosmic being, he chooses to use his wish to resurrect his daughter right before he dies. Jane Foster promises Gorr with her own dying breath that Thor will take care of the child, and Thor, now heartbroken and alone, chooses to adopt the child.
As explained in this article, she is Gorr's daughter, brought back to life through a request to Eternity and then adopted by Thor. She becomes the daughter Thor raises as his own one, and they will be known as Love and Thunder.
As Thor's firstborn and strongest child, Magni was a very powerful Norse God, though only regarded as a minor Aesir by Mimir. As such, he is still surpassed by his grandfather Odin, father Thor, uncles Týr, Heimdall and Baldur.
Like Stormbreaker, Mjolnir also allows Thor to wield thunder and lightning; however, it's not capable of summoning the Bifrost. The magic hammer did develop a power Stormbreaker couldn't, though, and it's able to detach its broken pieces to attack multiple enemies at once, before coming together again.
The two brothers, clouded by pride and hate, send the Destroyer after Jane, despite the new Thor saving others and fighting for what's right. While she gets thrown around, Thor refuses to back down, which is another reason why Jane is worthy of being Thor.
In the film, Mjolnir “chooses” Jane not because of her own worthiness, but because of what we see in a flashback to when she and Thor were still a happy couple.