Miguel could never have you in his own universe, so he searched through many universes until he found one where you were with his variant. However, that variant was toxic and abusive towards you, so he didn't hesitate for a second to take his variant's place to be with you

"Mi vida, you have no idea how happy I am to have you"

He said, embracing you, but he stopped himself as he realized that acting like this might raise suspicions

"I mean... I know I've treated you poorly, but I want to change for you"

He said, so you wouldn't suspect that he was a different Miguel