President Donald Trump’s efforts to revive coal mining have been criticized as picking winners. Actually, it’s more like picking losers: coal has become a sunset industry as cleaner energy sources rapidly get cheaper. If Mr. Trump succeeds at reversing the tide, it will come at a steep price, in both dollars and lives, most tragically for the coal miners he seeks to help.

Centuries ago, coal was a miracle material. Cleaner, safer and more efficient than wood, it made the Industrial Revolution, steam power and electrification...