Dems, centerleft and progressive, messed up by not going hard for ranked choice voting.
One of the biggest problems the dems had was third parties taking dem votes and not doing much but effectively acting like spoilers. Center-left Dems decried progressives for not voting blue no matter who, progressives were upset with the DNC for not being solid enough on Palestine.
This entire problem could've been prevented if the DNC worked as much on ranked choice voting as they did on gun control. People who voted third party would be able to vote support the lesser evil without completely selling out.
It wouldn't be that hard either. If anyone said this was influencing the vote (i.e. Heritage foundation) they could point out that the only change is that it more accurately reflects the will of the people. Even conservatives opposed would have to be intellectually honest enough to concede that it's different from outright fraud.
Sure now Republicans have gotten more eccentric, but this could've easily been advocated for in the 90s. Especially since even without attention there's been success stories in Maine and Alaska, showing bipartisan support.