"Death of the Liberal Class" by Chris Hedges is a good primer.
Thanks for the recommendation! Just went over to Amazon.
Obama, the so-called most progressive President ever, was completely captured by corporate interests and the market cheerleaders. He was funded and pushed by them. His campaign was staffed by Ivy Leaguers, technocrats, business executives, and Big Data wizards. Remember, Obama was the one who signed off on TARP in 2009, but he had zero idea how to fix or regulate things.
Obama was also POTUS during the Benghazi incident (although Hillary was the real face of villainy for that one) and he bungled the Dakota pipeline protest, being retarded enough to allow the incompetent LEOs to bring in anti-airplane artillery to... I don't know... scare some randos?
Obama only got elected for three reasons: Bush sucked and was a laughing stock by the end of his presidency, he was young, he was black.
For my two cents, I think there are a ton of factors involved in what killed the left.
1. The Democratic royalty were tainted.
The Kennedys were engrossed in scandals and conspiracies, and the Clintons were total trainwrecks. While I recall meeting a guy at our local Republican primaries who said he was there because the left had lost its way (and that's partly why I was there, too), I think there were still a significant number of Democrats who were very happy with Obama. Unfortunately, Obama didn't leave a dynasty, unless you count Biden.
2. Inflaming the culture war and the start of media manipuation.
When Obama was elected, any criticism of him from the right was chalked up to racism. The Tea Party movement that was started by Ron Paul supporters and planned well in advance of Obama's election? Racism. Do you not like how Obama reneged on his promise to end the War on Terrorism and instead decided to just follow Bush's original timetables? You're just racist. Mad that Obama promised to put every bill online so you can "read it before I sign it" and then immediately urged Congress to sign a massive bill that no one had time to read because the housing crisis meant there was no time for transparency? You sick racist!
The media also started really manipulating things around this time. I remember CNN(?) showing a picture of a guy with a rifle at one of the Tea Party protests and screaming about racist whites. The photo didn't show the whole person, just his leg and the rifle. Why? Because it was a black man who came to the protest with a gun to take a stand against big government and foreign wars
They also filmed a black Congressman walking into the midst of angry protesters, who would have been there shouting and shaking their fists at literally anyone who came out, and said it was "just like Selma". That crossed the line for a lot of people and showed that the media was trying to control the narrative.
To see what this lead to, just watch any left-wing outlet denying that Biden was anything other than a drooling dementia patient who needed a constant caretaker.
3. Purity tests.
Once upon a time, Democrats and Republicans disagreed more peacefully with each other. They didn't view each other as mortal enemies like they do now, but the left no longer stands for any diversity of thought, even within their own party.
Think of it this way: when Ron Paul ran as a Republican, despite being a Libertarian, the old guard didn't like it and went way out of their way to silence him. However, they eventually came to realize that Libertarians were going to infiltrate the party, and they could either tolerate them and work to find common ground or push them (and their voting power) away. As a result, Republicans come in a large variety (neocons, MAGAs, Libertarians, anarcho-capitalists, etc.), so you really have to go issue-by-issue when finding a candidate to support. They're allowed to debate each other and disagree and aren't quite the terror they were in 2008 and 2012.
When the left got invaded by socialists, they proceeded to do what socialists do: control the thoughts and behaviors of others. Because of this, you can get situations like JK Rowling's. Rowling was a good liberal who parroted all the correct talking points and believed all the correct things, until one day there was a line she couldn't fully cross. As they sing in
The Book of Mormon musical, "You cannot just believe partway; you have to believe in it all."
If you can't get behind everything, the left doesn't want you. In fact, they'll tell you just how racist and transphobic you are, which makes people just dig in their heels. They aren't interested in a conversation, they want to shame and dominate.
It doesn't help that they get more and more extreme. Abortion vans at the DNC? How about you guys go back to focusing on foreign policy and your retarded Keynesian economics and stop making these social issues the end-all-be-all of your ideology? This is how we got retards like Kamala Harris and Tampon Tim running for office.
The Republicans aren't exactly shining right now, either. But at least they aren't trying to shut down anyone who goes against their core platform.
And they haven't turned into this: