President Donald Trump promised during the campaign to bring back coal mining jobs, which U.S. Bureau of Labor Statistics data show have been declining steadily for decades. Once Trump became president, he issued an executive order and Congress passed legislation he insisted would revitalize the coal industry.

There are just two problems with that belief: declining demand and increased mechanization.

John Oliver on Sunday used his show, "Last Week Tonight," to break down the reasons coal has declined over the years and why Trump’s plan likely won’t make a difference. Trump has blamed Obama-era regulations for the declining coal industry even though the decline began decades ago, Oliver noted.

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Trump claimed President Barack Obama conducted a “war on coal” in a 2014 tweet without defining what that meant or how the "war" was conducted.

At a campaign rally in West Virginia, Trump told coal miners in the audience to “get ready because you’re gonna be working your asses off.” In addition to the executive order he signed in March to dismantle the Clean Power Plan, he withdrew the United States from the Paris Climate Agreement, which required the U.S. to lower emissions that cause climate change.

But even with those steps, few of the jobs likely will come back. As clean energy options have gotten more efficient and cost effective, coal has become less attractive. Solar and wind installations are up, and the country is seeing record-breaking output from clean energy options. In addition to an increase in wind and solar power production, the method of gas extraction commonly referred to as fracking has led to a boom in natural gas production.

Read: Carbon Emissions Cut In US BY Slashing Coal, Warm Weather

Oliver took a dive into the actions of the business moguls behind the coal industry, concentrating on  Robert Murray, founder of Murray Energy. Murray, who denies carbon dioxide is a pollutant, presented Trump with a plan for bringing back coal and overturning some Obama regulations, the Guardian reported.

In wrapping up the piece, Oliver said Trump “needs to stop lying to coal miners,” specifically he needs to stop telling miners their jobs are coming back, stop telling everyone that coal is clean and stop ignoring the industry is going through a difficult period.

You can watch the entire "Last Week Tonight" segment on coal here: