Re: It's not "why", it's "how"
The popular vote, that's irrelevant, the candidates campaigned for the electoral college votes because that's what matters. You simply cannot claim with any veracity that if the candidates had in fact campaigned for the popular vote that Clinton would have won.
And Obama won in 2012 with pretty thin majorities in a number of states.
Face it, we're all lucky to escape the rule of the kleptocratic oligarch Hillary Clinton. Kotkin is right about her being the crony capitalist to top all crony capitalists.