It's a mystery.
Bill Clinton isn't sure why coal country hates Clintons now.
"We all know how her opponent’s done real well down in West Virginia and eastern Kentucky because the coal people don’t like any of us anymore. They all voted for me. I won twice and they did well. And they blame the President when the sun doesn’t come up in the morning now."
Might be they blame him for pledging to wipe out coal? And there's Hillary Clinton talking about how "we’re going to put a lot of coal miners and coal companies out of business."
That might have something to do with it too. People generally don't take too well to being put out of work.
Then there was Bill Clinton's own 1999 attack on coal plants. It wasn't until the Bush years that the war on coal set off by his administration died down. And if left plenty of hard feelings.
Coal country hates Clintons. Even in the Dem primaries, Sanders won in West Virginia and the Kentucky primary was likely stolen from him.
People seem to take having their way of life eliminated personally.