

Bernie is a Zionist and not a socialist at all. He sucks and if he was in a general election in 2028 I probably would still vote for the PSL candidate because I don’t live in a swing state.
But he absolutely was screwed out of the 2020 nomination in a concerted effort from the Democratic Party establishment to get anyone but Bernie to win.
Elizabeth Warren stayed in the race until Super Tuesday to act as a spoiler while all the other moderate candidates dropped out and endorsed Joe Biden. The media consistently downplayed Bernie’s early lead.
Pete Buttigieg had shady connections to the owners of the app used to conduct the Iowa Caucus. That same Iowa Caucus held “votes” that were based on how loud the audience’s cheers for each candidate were.
The media buried the Tara Reade story (CNN even took down an old episode of their radio show where Tara Reade’s mother called asking for help because her daughter had been assaulted by her boss who was a politician in DC).

https://www.marxists.org/archive/lenin/works/download/what-itd.pdf
https://www.marxists.org/ebooks/lenin/state-and-revolution.pdf
tldr build parallel power structures under the purview of a revolutionary socialist organization outside of the current bourgeois democracy. Strengthen them and grow them out as long as the bourgeois state allows, then in a moment of crisis seize state power to oversee a transition from capitalism to socialism.
There’s also the anarchist strategy which is similar in essence but with the crucial difference of laying out the parallel power structures horizontally such that no central power nor state organs exist.