This is entirely based on speculation, but...
Until recently the anesthesiology program there had serious problems with work hour violations. I'm talking consistently in the 90s approaching 100. The residents were being taken advantage of, unhappy and seriously overworked. Now that is sort of fixed because they were in risk of losing their accreditation. They still work super hard because the crna crew is small so they get stuck with lots of mundane bs cases.
....maybe surgeons were going through something similar and had lousy work conditions/ hours? I have heard that yale in general is pretty malignant across the board, including surgery and internal medicine as well. Not sure how accurate this may be. Sample size of like n= 3, including 2 people who interviewed in the past there for surgery residency and "heard" from people at yale. They chose to train elsewhere.