Because it's a jarring genre shift and one they could have explained in-story but didn't. If you watched an episode of Glee and no one sang for the whole episode, you'd want an explanation for that too.

Well that's Angel for you. Always picking the most melodramatic ineffective course of action available to him.

I can agree to disagree on Buffy, but c'mon, no hate for Angel? Anyone? He was always Broody McFeelSorryForSelf, but he really jumped the shark when he tried to murder a helpless Wesley in the HOSPITAL. I guess maybe the insufferableness of Connor distracted from how irredeemable Angel was?