It felt like being put through a millennia of pain. Watching Jane die over and over again had been heartbreaking the millionth time as much as it had been the first time. But eventually it was a heartbreak that Thor grew numb to and when that happened? Suddenly it was Pixie in Jane's place. Once that grew tired for the demons torturing Thor, Torunn replaced her. Then Jake. His parents. Loki once more.
They found it hilarious, to break him again and again. They relished in the suffering he brought down on himself, all because he couldn't let go of the guilt of not being able to save everyone. Anyone.
But then something changed. Maybe it was Pixie's words as she came down to talk sense into him, while dusting the demons in charge of his loop. While they saw unicorns and imagined their skin melting off, her words of reassurance about him started to seep through. Or maybe it was when Torunn brought down the might of her lightning abilities and fried his torturers. As they sizzled and burned, her screams of him not giving into this Christian version of guilt when it came to his personal trauma started to break through the fog that kept his loop going.
Or perhaps it was Jake, who was quickly becoming one of his greatest loves in his centuries of life. Him with his reasonable and logical explanations to the demons that this wasn't the way to do things, that it wasn't right to put Thor through this when he was better off dealing with his personal guilt in less traumatic ways.
Though Jake's calm demeanor changed when they laughed in his face. Having a short Librarian lodging a magical axe in one of the demons' heads definitely changed their mood for the worst.
More likely it was time and all three of their words and actions that made Thor see things differently. Slowly, he came to realize that Jane's death was tragic, but she made that choice. His parents made their choices. Even Loki made his choice, to go out in a blaze of heroic glory doing the right thing.
So who was Thor to deny their choices? It wasn't his place to cast down on their decisions. They died nobly and he would just have to respect that. They all changed his world and the universe for the better with their choices and he would keep them alive in his heart while they took their next steps in Valhalla.
When he accepted that this was how things would be and he became ready to move on, the scene reset once more. But instead of anguish as Jane laid dying in his arms, he felt nothing but love and light as she disappeared into the universe. In her place, came a vision of his own next step in life:
As he wound back into the pantry he had been taken from, Thor smiled as he started to think to himself about the changes he would have to make to make room for the young girl that would be coming their way.