Spider-Man: Far From Home Trailer - The REAL Reason Nobody Mentions Infinity War?
2. The MCU & Trauma
The MCU has a rich vein considering trauma, and not at all by accident. It plays into a considerable number of character arcs. Black Widow and Hawkeye were the marks of their black ops service (Widow even says she has "red in her ledger" she needs to wipe out); Odin is fundamentally changed by the impact of what he did alongside his evil daughter before Thor's birth; Bruce Banner exiles himself when he's haunted by what Hulk could do when he loses control.
On top of that, Scarlet Witch (and her dearly departed brother) is superpowered precisely because of past trauma. Their family was killed and they found their way to HYDRA looking for a means to gain revenge on The Avengers. Zemo likewise is compelled to bring about their end because of the trauma they caused to him in Sokovia when his family were killed. And then there's Tony Stark, a walking, talking poster boy for past trauma.
Not only was he shaped by the death of his parents - enough to use the last time he spoke to them as the "traumatic memory" in his demonstration of the BARF technology - but he suffered PTSD thanks to the Battle Of New York. From that point on he was - as Thanos put it - "haunted by knowledge" and by the image of the end of the universe and his friends that Scarlet Witch implanted into his head. Every decision he makes from then on - disastrously in a lot of cases - is because of his trauma.
And crucially, Tony's trauma is often based on things that didn't actually happen. He suffers PTSD more pronouncedly than the other Avengers in the wake of the Battle Of New York because he chose to die to save New York and Earth by closing the portal and nuking the Chitauri fleet. It didn't matter that he avoided that, he was still as profoundly traumatised by it. Likewise, the image Scarlet Witch uses to destabilise him isn't real, but he cannot avoid the emotional and psychological toll on him.
Really, when Thanos told Tony he too was haunted by knowledge, he gave us the key to this Far From Home conundrum. Because those words reveal the impact a snap would have on those who were killed and those who witnessed all of those deaths. They'd be haunted by the experience and by that knowledge. How you'd escape knowing what it felt like to disintegrate is beyond the realms of conventional knowledge. It's the kind of thing that breaks minds entirely.
There's only one possible answer. They don't experience it at all.