The theorist continued: “Odin knows that when he dies his magic will be lifted, and Hela will be [able to] break free from the dark magic that imprisoned her.
“What he didn’t tell Thor is that Odin’s enchantments on the Mjölnir will also be null after his death.”
Of course, Thor’s hammer is still incredibly powerful, but no longer the invincible weapon it once was.
With no time for Thor to process his father’s death, Hela shows up and destroys Mjölnir before the Bifrost transports him to a junkyard planet.
source: express.co.uk