Bernie bro equivalent

[Samof94]

Why wasn’t there an 00’s equivalent to this, especially in the first half of the decade?

[I spent the winter writing songs about getting better]

Because Bernie Sanders hadn't run for President.

[wimp]

Why wasn’t there an 00’s equivalent to this, especially in the first half of the decade?

Daily Show liberals maybe?

[darklordoftech]

Nader Bros?

[Samof94]

Nader Bros?

There could have been. Imagine if had run in the primary against Gore and done well. Gore wasn’t as hated as Hillary though.

[Bleach Blonde Bad Built Butch Bodies for Biden]

Quincy Adams Bros were a pretty ruthless bunch in their personal attacks against Jackson, specifically his wife. Jackson himself might have been a scumbag (and JQA was too good a president for his era), but the attacks against his wife were completely uncalled for and even led to her death.

[Agonized-Statism]

Political apathy was big then. Millennials were forged in the misery of the late 2000s, awakened by Iraq and the Great Recession, and first came into politics in a big way with Obama '08.

[Kleine Scheiße]

the big answer nobody wants to hear is ron paul

[Okay, maybe Mike Johnson is a competent parliamentarian.]

the big answer nobody wants to hear is ron paul

Including some of the literal same people as Bernie's 2016 campaign.

Idealistic "Ron Paul, man!" early-2010s 4chan dwellers are in the DSA ecosystem now; cynical ones are on Gab.

[H. Ross Peron]

Clean for Gene.

[Thank you for being a friend...]

I still wonder what Bernie Bros are.  Are they basically progressive frat boys?

[Big Abraham]

I still wonder what Bernie Bros are.

They're nonexistent. It's a pejorative term made up by the Hillary-pilled media that serves no other purpose other than to denigrate Bernie Sanders and his supporters.

[Klobmentum Mutilated Herself]

The Deaniacs should be so obvious I'm surprised only one person mentioned them.

[Orser67]

I still wonder what Bernie Bros are.  Are they basically progressive frat boys?

I think the Wikipedia article is a good starting point for understanding the term's usage (whether or not one agrees with it).

Robinson Meyer, a writer for The Atlantic, coined the term Bernie bro in an October 17, 2015 article[2] to describe young, white, progressive men who, in his view, believe that "The only reason you, and every other Facebook user, haven’t supported Bernie yet is your own willful ignorance". In the article, Meyer characterized "Bernie Bro" as "male... white; well-educated; middle-class (or, delicately, 'upper middle-class'); and aware of NPR podcasts and jangly bearded bands." Furthermore, according to Meyer, "[t]he Berniebro asserts that this country needs highly principled, pie-in-the-sky progressive policies, regardless of how likely they are to become legislation.

To answer OP's question, I think a big part of the answer comes down to the increased prominence of social media in the late 2010s as compared to the early 2000s. To be clear, there certainly were liberal blogs like DailyKos and groups like MoveOn, and in fact the Iraq War mobilized the online left from 2002-2008 in a way that's somewhat similar to the way Trump mobilized the left from 2016-present. But social media engagement has grown dramatically in the 21st century for various reasons; most importantly, only about half of American adults even used the internet in 2000. I would argue that this social media has had a major impact in amplifying the voices of people on the left wing of the Democratic Party and the right wing of the Republican Party.