I'm going to pick at this one for some fun. Here's a few key underlying assumptions for your post.
0) This is more of a side point, but your use of "We" stands out. There is in fact no "We". You personally were not involved in any aspect of planning, executing, or strategizing the national campaign so you were not in any sense part of the "we" that made strategy mistakes. If you mean "we" as in the greater Democratic party that group solidarity doesn't really exist either. The party bosses have demonstrated repeatedly through both words (e.g. "You need to have a public policy position and a private policy position") and through actions (e.g. attempting to railroad both Sanders and Cortez) that they don't give a flying fuck about what you the individual progressive voter thinks either individually or collectively beyond whether or not you vote for them. Ironically enough your comment about other people being "ignorant" is exactly how they view you: too stupid to understand why corporatist policies need to be maintained.
1) First false assumption is that "we really underestimated how much ignorance there is". Quite to the contrary, what information is publicly available (memoirs, leaked emails, insider books, interviews, etc) indicates that those responsible for the DNC's strategy largely regarded the majority of the American public having a level of intelligence that equates to being mentally retarded. This assumption made them act with an almost mind-bending level of hubris that assumed that voters in key swing states were stupid enough to vote for whoever the advertisements and pundits told them to. As it turned out that wasn't enough.
2) The bigger problem is that almost every single person who voted for Trump is acutely aware of the fact that you (the "we" you mentioned) think that you are much, much smarter than them and that they're really, really, stupid. This doesn't persuade anyone. It just makes them hate you for being a pompous jackass. Even the freaking New York times pointed out that this attitude is hurting the cause.
General social tip I've learned from my perspective. Keep in mind that as someone with a top 0.1% SAT score, voted smartest person in the class at a top 20 business school, and got the highest on my high schools IQ test I COULD play the "I am Very Smart" game better than almost anyone except MIT/Standford valedictorian types like my little brother. In practice there's two reasons I don't. First it doesn't necessarily translate into any subject matter competency (the guy with the highest IQ in the world supposedly is a bouncer). The second reason is that Walking around thinking you're smarter than everyone else pissess people off.
That last thing is one of the single most important lessons that the left needs to learn. A little bit of humility goes a long way and would probably deflate Trump's balloon entirely.
If you won't take it from me, take it from this guy who absolutely hates Trump
Side note: This is the exact same reason why Republicans are making a severe mistake with Cortez. Attacking her for being "stupid" doesn't persuade anyone (although I personally find her ragingly ignorant) because it both triggers the same resentment I just talked about and because it inspires a reaction where left-leaning males can rush online to save the damsel in distress from those Right-wing bullies. The problem they have is that as she is a credible change candidate and an attractive female that she can get away with an enormous amount that no old-white, corporatist DNC politician can.
FOX News can't help themselves because it gets ratings but the smarter political strategy would be to just ignore her.