Your naivety knows no bounds @Dexter ! The second she stops being a useful idiot she will be dispensed with.
Dexter has a point. AOC is popular because her ideas are popular with a large, evergrowing segment of the Dem Party, the youthful Dems.
It would be one thing if she were the only Dem spouting Marxist nonsense, but you have the example of Bernie Sanders, an avowed socialist, coming close to getting the Dem prez nomination in 2016 only flouted by Hillary Clinton's shenanigans with primary rules in the Dem Party. And Liz Warren, Cory Booker, and Kamala Harris are saying similar things like Sanders and AOC.
I'd like to think mainstream Dems are rational and sane, but they'll go with the flow. If everybody else in the party is touting socialism, they'll do it too.