The difference is that there's currently no large-scale acceptable replacement for oil, so ditching oil would be committing a global suicide (or genocide, if you will), while ditching coal in the presence of nuclear, wind, solar and hydro plants that can replace it much more seamlessly is merely a reasonable thing to do at this point.

In addition, this is apparently an investment fund and the coal stocks are tanking, what would you do with the money of the people who turned it over to you for safekeeping? Keep it there?