A few more details in this Fortune story about the short-lived coup against Matt Mullenweg, but still no real explanation for why it happened:

A remarkable level of secrecy surrounded the drama. None of the board members have publicly explained why they suddenly wanted him out of the company. Mullenweg has declined to describe why he was all but fired, or how he quickly got back control of the company.

You come at the mad king, you best not miss.