A new Avengers: Endgame theory explains exactly why only Tony Stark’s Iron Man was capable of defeating Thanos and his armies during the Battle of Earth. Bringing the MCU Infinity Saga to a close, Avengers: Endgame detailed Earth’s Mightiest Heroes’ last stand against Josh Brolin’s Mad Titan, Thanos, after he snapped away half the population of the universe five years earlier. Robert Downey Jr’s Iron Man was pivotal to this mission, as his discovery of time travel allowed the Avengers to embark on the Time Heist to collect the six Infinity Stones.
https://screenrant.com/avengers-endgame-theory-only-tony-stark-iron-man-snap/