It's crazy. The Fox execs warned him that "they would not tolerate any unprofessional behavior" before he even started. So they were willing to take a risk on him knowing he could implode at any point.
I'm sure there's an exposé coming, and he's been contacted over the past few weeks to respond to various claims as journalists vet stories from his alleged victims in preparation for pieces. He has a longstanding rep for being unstable (remember Halle Berry reportedly telling him to "kiss her black ass" on the set of X-Men?), so the coming bombshells have to be pushing him over the edge.
Speaking of Singer AND Spacey, look at this: