In short, like the girl working at the drugstore who was noticed by a producer and became a starlet, AOC got lucky.
Not by intelligence, that's for sure. Or by patient and diligent study. She did get lucky.
But nobody really thought she was going to beat a top House Democrat, so whoever was staking her early on probably didn't give her much or expect her to get so far so fast.
So luck, and what you could call charisma. Also a lot of energy and an instinct to run to where the cameras are, and an uninhibitedness - a lack of shame or embarrassment.
“... an instinct to run to where the cameras are, and an uninhibitedness - a lack of shame or embarrassment.”
Basic qualities of a Democrat politician.