Yes he did. There are several videos posted on You Tube this morning showing his remarks at the beginning of the program. They then broke for a commercial, and when they came back, Steve Kornacki had taken over and finished the show. I don't know if Matthews blindsided the network, or if he was told just before air time to say goodbye and leave. When Kornacki came on, he clearly had the "deer in the headlights" look. I got the impression Kornacki had no idea this was about to happen when somebody grabbed him and told him he had to get on the air right away.
Well I only regret that Matthews apologized. I didn’t see the incident with a female reporter but apparently it involves him complimenting her on the air, it wasn’t something he did behind the scenes.
Interpreting his sudden resignation, I think he decided that he’s been a loyal Democrat mouthpiece for many decades and when they decided to turn on him he decided they can go to hell. I wish he didn’t apologize.