Thor's Stormbreaker versus Mjolnir: Thor wasn't the first to wield the Thanos-killer in Avengers: Infinity War and there's a reason why

The recent launch of digital versions of Avengers: Infinity War has led to a number of revelations that may shed some light on the questions that fans have been asking since the superhero blockbuster released in May.

The reason for this isn't just that the film can now be watched repeatedly and at leisure, but also because it contains special new features and commentary by its directors, the Russo brothers. 

One particular aspect of the film that they have elaborated on is about Thor's new axe, Stormbreaker, and how Thor wasn't the first person to wield it.

Here's a little background:

Since Thor's debut in the Marvel Cinematic Universe in 2011's Thor, and his hammer Mjolnir's debut in the post-credits scene of Iron Man 2, the two have been intrinsically connected. Basically, the theory is that only a "worthy" person can lift Mjolnir, which is described as the greatest power in the universe. When Thor shows himself to be a bit of a warmonger, and not entirely worthy at the start of Thor, Odin, his father and King of Asgard, tosses him out of the realm eternal and casts him out to Earth, where he loses his Asgardian powers and immortality. Even when he comes by Mjolnir, he isn't able to move it an inch, until it returns to him once he proves himself.

Thor uses Mjolnir's apparent infinite weight in battle, with the likes of Hulk, Loki, all the Avengers (save for Captain America, who can only just move it) and even a dragon-beast on Surtur's planet unable to dislodge it once he leaves it somewhere. However, two people, apart from Thor are shown to be able to do with Mjolnir what they will, as the newly-'born' Vision can lift it in Avengers: Age of Ultron, and Thor's sister Hela stops it in mid-air and then shatters it to bits in Thor: Ragnarok.

After losing Mjolnir, Thor demonstrates, for a time, that the hammer was simply a focus for his power and not a source, but come the start of Avengers: Infinity War, as Asgard's remnant is attacked by Thanos and his 'children', it becomes clear that Thor, in his current state, can't take on the mad Titan.

After being rescued by the Guardians of the Galaxy, Thor sets off to Nidavellir, where Eitri the dwarf forges the universe's most powerful weapons using the power of a star. On reaching there, however, Thor discovers that Thanos was one step ahead of him and used Eitri to forge the Infinity Gauntlet, which could harness the power of the Infinity Stones. To combat such unprecedented power, Thor seeks a Thanos-killer, and Eitri has just the thing -- a weapon for Kings, meant to be the most powerful in Asgard. This one is an axe and it's called Stormbreaker. What's more, it's supposed to theoretically be powerful enough to summon the bifrost, which Asgardians used to travel between realms.

There is reason to believe that Stormbreaker was also forged with the essence of Thor, as while opening the crippled forge mechanism, the star's power went right through the Thunder god, almost killing him.

What's the dispute: Fans pointed out to the Russo brothers that despite the complex backstory of the super-powerful axe, which proved to be just as effective as touted as it overwhelmed the combined power of the Infinity Stones and almost killed Thanos, Thor wasn't the first to wield it. That person was none other than Groot, who, as Eitri was searching for the axe's handle, put the two pieces together and fashioned a handle out of his own arm.

So was Groot worthy? Apparently, not.

As per the Russo brothers, "worthiness" is not a requirement for wielding Stormbreaker.

So can anyone use Stormbreaker: Thor was clear that only beings of extraordinary power could wield it and that if the Guardians (morons) tried, they would lose their sanity. However, Thor probably doesn't know at this point that Star-Lord is part-Celestial.

But there's an answer to that question too:

So others can use it too! But will they? We'll find out in the next year as Captain Marvel and Avengers 4 wrap up the current arc of the Marvel Cinematic Universe.