I’d like to tell you that President Donald Trump’s election in 2016 kickstarted a journey for the Democrats toward the hard-left and that their perception of Trump as a radical is what caused them to radicalize themselves, but that wouldn’t be accurate.
The Democrat party has been on this journey for decades and began it in earnest around the 1930s with the founding of the Frankfurt School and the spread of critical theory. The Democrat party became infected by this ideological nonsense and as time progressed, you can see policies rise like fungus caused by critical theory and Marxism over time.
For a time, this infection kept to the fringes of the Democratic party, but it kept opening the door to spread it with every election, every social issue, and every opportunity to gain leverage over their Republican opponents. Even the Republicans weren’t wholly immune to it.