No, he does not seem surprised as he had his mind made up about an important life decision and a carefully crafted resignation letter ready in a matter of hours.
> carefully crafted resignation letter
Are you trolling, the letter is short and all lowercase lol
Maybe he used ChatGPT to write the letter.
I think if he didn't know why, he would wait to find out what the story was.
Instead he knew enough to make is call immediately, knew what he was going to do.