Down A Dark Path

SPOILERS FOR ENDGAME IN SUMMARY
[Also please note that I have not read the Doctor Strange comics and don't have a way to do so at this time.]

Time can affect the brain in so many ways. People change so often that they don't even notice it's happening. Bad people can become better and even become a good person over time. The opposite is also true; a good person, over time, can change into a bad one.

Stephen hadn't noticed it at first but when he did he was so far gone that he no longer cared. After living through countless death's at the hand of Dormamu he also lived out many million different possibilities. Experiencing constant battle for so long with no rest changed him. Through seeing so many possibilities he also saw many sides to the people he fought alongside. Foolishly his heart latched onto Tony Stark, at first he found him irritating...then respected him...found that Tony understood his issues...then he began to care.

However this man was going to die.

Thing's played out as they were meant too and Stephen latches himself onto Tony's chosen family. He made sure Peter stayed safe when he went out patrolling and even gave him tips on hand to hand combat. He visited with Pepper and spoke with her about the various possibilities he saw as well as shared tea together. He would take time to not only tell Morgan stories about her father but would use his ability to show her the stories as he told them. He offered to teach Rhodes the mystic arts so that he would be able to walk on his own should he choose to. He would often meet with Happy, with Morgan in tow sometimes, at a burger place.

He felt guilty at his failure, he pinned over the man for a long time.

Then something snapped.
So here Stephen is, breaking so many rules just so he could change Tony's fate. He would have to change many others to ensure Tony lives but that's alright.

The world needs Tony Stark, no if and or but's about it.