Then the Dems just went like OK we’ll never ever do something like that again.
I mean, it's because instead of pulling the DNC left. He just abandoned it because it was a relic of the past and it was easier to just ignore the DNC and let state parties handle their own shit.
His mistake was not completely burning the DNC down. So after he left office and moderates retook control in 2016, they've made a lot of moves to ensure a moderate or Republican are the only two options.
People talk about how much Obama pissed off trump.
But its nothing compared to how much Obama pissed off "moderates".