I would argue serving 19 years in the US Senate is a far more impressive political accomplishment than being elected mayor of a city, even one as prominent as New York. Bernie has had immense political success, even if his attempt at being nominated for the presidency was narrowly thwarted. Cuomo may have been an insider, but he was a disgraced insider; there's no comparison to the political figures who beat Bernie.
Yes, I would argue that Bernie's excellent career lent him an air of credibility that other politicians just don't have. But the discussion was about whether online popularity translates to real life, and I'd argue that it certainly didn't for the Bernie candidacy at least not enough to win.
Online is just another component in the political game. We saw all this nonsense in 2024 yet again. I'm kicking myself for having fallen for all these pollsters, some of which have had an impeccable perfect record for decades and yet still managed to get it wrong this time around.