Former engineering powerhouses like HP, Boeing, and IBM slowly get hollowed-out into incompetence when it’s assumed that Engineering and technical skills don’t require a considerable depth of knowledge and experience.
could it also be the normal generational rotation of people through the organization?
Everyone grew at a tremendous rate since the 1960's. Many, many more engineers. And then they retired.
The most effective leadership for a technical company is leadership with actual technical creds to back it up.
The technical side is a must because you need someone who actually understands the business and the innovations that must takes place. But you also need someone who can provide the people-leadership skills and the business wheeling&dealing.
These are all crucial skills and take up a persons time, so it’s not uncommon to see this come in the form of a duo (Apple and Steves, or Microsoft with Bill+Steve).