I think the bigger factor is the fed shutting down a lot of coal fire power plants, reducing demand for coal even more.
Interestingly, the newer coal-fired power plants that still use low-sulfur Powder River Basin coal are still going. But those power plants that use high-sulfur coal—many of which are several decades old—are starting to shut down, especially now with cheap natural gas (natural gas-fired power plants are going up everywhere).