Coal was king, note the change in tense.
The four largest coal companies were worth a combined $21.7 billion dollars in June 2010. Now they’re worth $1.2 billion
Coal was attacked by other fossil fuels that found technological advances, like fracking. As the competitors’ prices dropped, so did coal’s profits.
Coal was also attacked by clean air standards, or as some see it, finally having to pay for the consequences of coal pollution.
Coal, like all fossil fuels, are being attacked, or supplanted, by renewable energies like solar and wind whose prices are down, and that aren’t polluting.