Warning: full spoilers for Avengers: Endgame ahead!
The filmmaker’s commentary track on the digital release of Avengers: Endgame has shed light on the abrupt and shocking death of Thanos in the first 20 minutes of the movie.
The scene takes place soon after the surviving Avengers locate the Mad Titan’s hideaway planet and capture him in an effort to secure the Infinity Stones. As we now all know, Thanos had already destroyed the stones, leaving the heroes without an easy way to undo the Snap. Upon learning this, Thor takes a hollow victory by lopping off the villain’s head with Stormbreaker. But co-writer Christopher Markus reveals that the Avengers were only able to kill him because Thanos allowed it.
Source: IGN.com Avengers: Endgame’s Shocking Thanos Scene Is More Morbid Than Anyone Realized