At this moment in the audio commentary for the movie, Joe Russo comments, "
See there, with his Gauntlet and the arm, the power that it takes to use all six Stones is significant, and clearly damaged the Gauntlet and damaged Thanos permanently." The Infinity Gauntlet was
forged by the dwarf Eitri in the star-powered forge at Nidavellir, since only a very rare and powerful vessel could possibly contain all six Infinity Stones (which, as we learned in
Guardians of the Galaxy, are so devastatingly powerful that ordinary beings cannot hold them without being vaporized). However, not even the Infinity Gauntlet could withstand the power of all six Stones being unleashed at once without sustaining some damage.