No doubt that Manchin would use whatever dirt against Blankenship, true or not.
But not everyone believes those stories you describe are true. Many believe he was railroaded by Obama prosecutors in their war on coal.
https://youtu.be/X8xu547cxGo?t=175
WVA, home of corruption left behind by dead democrats like Byrd, is a state where democrats will falsely accuse you of killing your mother and have their union goons organize media to pound it into voters as fact.
Massey had a massive history of safety issues before he left. He didn’t care a whit about his men. I’m not saying the UMWA is great, but Blakenship certainly let safety lax.