In the Marvel Cinematic Universe, the Infinity Stones are treated with great significance as they represent the fundamental foundations that began the universe. As a result, they carry immense power both scientifically and spiritually. The full range of these stones have been featured throughout The Infinity Saga, ranging from emitting massive amounts of radiation to even having mystical properties. But when they are together, they are almost unmanageable. That said, why could Thanos pull off this feat without succumbing to its negative effects before cracking?
In the comics, Thanos is an Eternal with a deviant gene. This is why he looked different from other Eternals and also possessed immense strength and other powerful properties. However, in the MCU, aside from being a sibling to Starfox, his legacy has yet to be fully explored. Therefore, it’s more likely that he was simply part of a Titan race and possibly stronger than his peers. But that alone could not be enough to overcome the immense energy given off by the stones. To do this, Thanos had to do a job that was both necessary to his goal and incredibly violent.
When the Hulk tried to use the stones, the gamma radiation badly damaged his arm, and the snap rendered him virtually useless. Considering he’s the only being able to physically resist The Mad Titan, it proved just how deadly the gauntlet could be. But for Thanos, his intelligence matched or even exceeded his strength, and he knew he would need to be physically prepared for his journey. To do that, he had to dedicate himself to being physically fit in the worst way imaginable.
Over the years, Thanos has used his belief in universal balance to motivate him. With each planet he grew stronger in both power and resolve. When the time came for him to wield the stones, he knew that the endless war had sharpened his mind and body to endure their effects. He also likely searched for every stone and its effects, preparing for battle. As a result, the army he brought with him to each planet was probably just a scare tactic, as he could have decimated an entire empire on his own if he wanted to.
The MCU’s Black Order may have played a part in his training as well since they each had skills and abilities that could help him train to control the stones. For example, Ebony Maw used telekinesis, which meant that Thanos’ mind had to be extremely strong to physically withstand Maw’s attacks. Meanwhile, battling Cull Obsidian would have given Thanos the strength he needed to fend off the Power Stone’s energy. Proxima Midnight and Corvus Glaive could have tuned Thanos’ mind and reflexes so he could counter every stone that invaded his body.
For years, Thanos was built to be one of the MCU’s most powerful and deadly foes, and that fear was entirely justified. Through research and bloody conquest, Thanos likely used his skills to hold back the Infinity Stones’ desire to tear him apart atom by atom before The Snap. So in the end, it was no surprise that it took cunning and heroic sacrifice to defeat an enemy who had molded himself to be the sole user of the Infinity Gauntlet.