While I'm sure DA can and will go into far more detail, this guy was one of the biggest industry leaders with regards to coal. He was pretty much literally the stereotypical Evil Capitalist Company Boss, perfectly willing and able to steal, lie, cheat and let people die for the bottom line of the company. Both through actions and by using money, he was instrumental in keeping the coal industry alive and profitable; keeping health and safety regulations out, keeping subsidies coming in, covering up wrongful deaths, suing anyone who dared to try and oppose him.
It's because of that last one, incidentally, that John Oliver sang that song. They did a show about Bob and the coal industry, Bob sued them, and eventually it was ruled fair use. Which lead to LWT to do a segment on SLAPP suits, ending with that song.
Insofar as you may or may not believe in such things, he was unequivocally an agent of Evil.