Hang on to your Tesseracts! Apparently, in Endgame[/em], when the Avengers traveled back to 2012 to swipe various things from the 2012 Avengers, they inadvertantly started a branch in time where Loki ended up with the Tesseract. Of course, once that occurred, the Time Variance Authority quickly spotted him as a Deviant and quickly recruited him to help in their fight against even more deviant Deviants.