Some management would be cut off when the time comes, Execs on the other hand are not there for work and are in due to personal relationships, so impossible to fire. If you think someone like lets say Satya Nadella can't be replaced by a bot which takes different input streams and then makes decisions, then you are joking. Even his recent end of 2025 letter was mostly written by AI.
If an AI exec reliably outperformed meatbag execs while demanding less $$$, many boards would consider that an upgrade. Why gamble on getting a rare high performance super-CEO when you can get a reliable "good enough"?
The problem is: we don't have an AI exec that would outperform a meatbag exec on average, let alone reliably. Yet.