You're assuming those people are far left in their ideology.
Bernie picked up tons of independents who actually skew more to the center or right in the US, especially the ones who often up end identifying as Libertarian, which is basically a right-wing party in the US.
Shocker - the centrist of all the new faces in politics picks up the centrists/conservatives. Tons of those profiles even have right-wing slogans in them about "MSM". Did you even look at who was replying?
I don't even think there's a new far left face in running for 2020, so this boogeyman and obsession with them by centrists in the wake of centrists causing Hillary to lose is so weird.
Kamala is Left, Jason is Center-Left and Tulsi is a Centrist with some wild as right-leaning views as far as I'm aware.
Hell, the main far leftists who even have a chance in 2020 are Bernie, who isn't going to run, and Sherrod Brown. Trust me, I'd love for the Far Left to have all this mythical political capital people are claiming they do.
Trust me. "rebels = terrorists" and "Assad = good" are not left talking points, they're right talking points. Politics in the US are a left-to-right spectrum that doesn't wrap around. There's no mythical overlap between the far left & far right. That ad nauseam talking point is stupid. The Far Left may be critical of US imperialism in the US, but it's just as critical of Assad and is still largely pro-people/pro-rebels/pro-Syrians.