This is depressingly plausible:
“Solid majorities of the nation, in other words, could vote for a Democratic White House, a Democratic House, and a Democratic Senate, and yet Republicans could gain control of all three.
The system is rigged. It was rigged from the outset, quite intentionally, to favor small states. Under current political coalitions, that’s become an enormous advantage for Republicans. The country’s framers obviously could not have known that they were creating a system that would give Donald Trump’s party an unfair advantage over Hillary Clinton’s party more than two centuries later. But they did create a system that favors small states over large states.”
I think there are more options than Ian Millhiser. But he’s got a good take on why we’re so fucked.