A Toxic Cover-Up? Slurry pond floor collapses into mine below. Environment disaster ensues.

Why Now. Why a year after the guy was fired?

Both occurrences happened on "Clinton’s watch".
The job of investigating the mine should have been easier the second time.

This guy was probably a career bureaucrat milking this job for all it was worth. After all, looking a hole in the ground isn't like assembling the pieces of a downed Airliner. The length of the investigation was not cited, just that it was "cut short"

Key Paragraph:

“Davitt McAteer was Spadaro's boss when the disaster happened, and head of the MSHA. He says Spadaro is right, that his own regulators hadn't done their job: “I know they didn't do enough in terms of enforcement because the thing failed. That's the proof.”