As someone who worked with the man for two years, this is very surprising to me. I never saw this aspect to his personality at all.
I do believe that his presence on comedy programs and his desire to be the most funny, engaging and interesting person in the room played a huge role in this, and it should have been monitored ahead of time.
The rank and file at NBC are really upset about this, and very angry at him for tarnishing their reputations by his actions. Clearly it will be very difficult for him to return to the chair, and based on what they are investigating, I don't think there's a chance in hell that he resumes his role as the anchor for NBC Nightly News.
What isn't happening, and should, is figuring out why the senior execs at NBC News and NBC Universal, namely former execs Andy Lack, Neal Shapiro, Steve Capus, Jeff Zucker and Bob Wright, and present execs Deborah Turness, Pat Fili-Krushel and Steve Burke did NOTHING to reign this nonsense in prior to it reaching critical mass. They knew of these issues, and ignored them because they didn't appear in the newscast. Now, they are on the hook for $45 million (the remainder of his contract), and likely do not have a way out of it without paying him to leave. They collectively screwed the news organization, and it's a real shame - there's some very good and talented people working there.