Coal has been dying since before president Obama. It peaked in 2007 and is dropping even faster recently. I point this our so that you can see that the impact on the economy of coal has little to do with the former president or those darn radical environmentalists. 

Further, there have been gains in the renewable and gas sectors, so that can be a net gain for states such as Colorado. Nationally, coal production employs around 70,000 people. This is fewer that the number Arby's employs. Finally, coal mining is not anywhere as labor intensive as it was. 

Simply put, coal is just not that big an economic deal any more.

https://www.washingtonpost.com/news/wonk/wp/2017/03/31/8-surprisingly-small-industries-that-employ-more-people-than-coal/