Assuming you're right and Satoshi did lose their private key, one thing I find implausible is assuming embarrassment. Satoshi was, for what we know, a pseudonym

Assuming you're right and Satoshi did lose their private key, one thing I find implausible is assuming embarrassment. Satoshi was, for what we know, a pseudonym that has held really well (we still don't know their real name). Personally, I'm embarrassed when somebody can acurately pin a weakness to my character that I feel vulnerable about. For example: Satoshi could have been playing a persona that they aren't in real life, similar to how an actor plays a role in a movie. In that case, if e.g. someone criticizes a personality trait of the movie role, the actor won't personally feel embarrassed since the critique doesn't fall back to their own personality. I believe the same logic is transferable to the case of Satoshi, where even if they lost the key, they wouldn't truly have to feel embarrassed consider that they've acted the online personality from the get go.