Carpe Libertatem
Member
Hillary actually did succeed at making inroads into Republican voters, considering her improved numbers with college white voters. The downside is that this gave up Midwestern working class voters and (probably, this is just an assumption on my part based on anecdotal evidence) helped depress young minority turnout, the groups she was already shakiest with.
Making inroads with Republican voters is not mutually exclusive with winning Midwestern working class voters. You can do both.
Mostly, the Democrats underestimated just how racist/sexist the latter group is. Hillary et al thought telling and showing them that Trump was a racist/sexist/etc was enough. Turns out they just didn't care and voted for Trump anyway.