Aside from the environmental degradation that results from mining coal and burning it for power production, Trump's insistence on reviving the coal industry by repealing environmental rules and regs doesn't make any sense economically. Coal is more expensive than natural gas, even without regulations. For many years utilities have been switching from coal to natural gas and that trend is only accelerating with the advent of fracking, which opened up more NG reservoirs and drove the already cheap price down further.

Coal doesn't have a future as an export either, since it's still competing with liquified natural gas (LNG). In other words, Trump is pandering to coal producing states solely to curry favor with, and get the votes of, those who work in the industry, even though he can't actually fulfill his campaign promise of bringing back jobs. Coal is dying and he can't bring it back.