MCU seemingly created a plothole when they showed Thanos grabbing the Infinity Gauntlet in the post-credits scene for Age of Ultron. This quickly became an issue as many fans pointed out the presence of the Infinity Gauntlet in the first Thor film.
However, this was explained in Thor: Ragnarok, when Hela was going through Odin’s vault. When she finds the Gauntlet, she throws it away saying, “Fake!”
Now, this does help to clear one plot hole, it also creates another. The question that remains is why did Odin have a carbon copy of the Gauntlet in his vault?
A fan theory on Reddit by user cgcs20 throws some light on this, stating that it was Odin who designed the Gauntlet in the first place. As learned in Ragnarok, Odin was once hungry for power as he continued conquering the world alongside Hela. However, he had a change of heart which sent Hela into a fit of rage before she was banished by Odin.
Now the user suggests that Odin went to Nidavellir and had the dwarves design the Gauntlet, as he desired to wield the power of the Infinity Stones. What we saw in Thor and Thor: Ragnarok was the same replica created by the dwarves.
However, after having a change of heart, Odin decided not to harness the power of Infinity stones but kept the model with himself to remind him of the man he never wanted to become again. This also explains the simultaneous disgust and happiness Hela exhibits while knocking the Gauntlet on the floor, calling it fake.
This theory makes sense and works on different levels. But only if there was a way to explain Thanos attaining the Gauntlet in Age of Ultron…