It turns out the timeline that the characters are currently living in is not the first, but the result of a wish from a previous timeline. A timeline where Tom Dupain wielded the Butterfly, was distant and bitter from the loss of Sabine, and managed to use the wish to get her back. Adrien and Marinette were still the heroes of that timeline, and they had been together, but the price rewrote the reality they knew, and took Emilie in exchange; leaving a once sweet and caring Gabriel to be the distant and desperate villain.

His Peeps — Shiratorizawa VBC

Bonus:

AU where Hawkmoth knows about the wish because he has done it once before- and the price was Emilie landing in a coma.