In The Killing of a Sacred Deer (2017), Matthew tells Anna about how he anesthetized Steven:
Matthew: You know an anesthesiologist is never to blame for the bad outcome of an operation. The surgeon is always responsible. He'd had two drinks that morning before we went in to prepare. Luckily no one else realized. I was the only one that knew.
Why does Matthew think that no one else realizing Steven’s two drinks was lucky?