Mr. Jones has left to pursue other interests. It turns out we hired another loser, and we had to pay him a bundle to leave quietly. Programmers rarely have that luxury.
New managers have a different kind of installed base to worry about.
While the difficulties they face are not as technically daunting as creating a backward-compatible operating system upgrade, the social engineering issues will present a manager who is taking over an existing organization with the company's own set of significant challenges. When you take over a department, whether it's through a promotion or a job change, you don't get the luxury of designing your operation from scratch. But where programmers usually have a test environment in which they can safely find and fix mistakes, managers have to do their testing in the production environment of an ongoing operation. Missteps are very public and hard to unmake. The social engineering starts before you take the job.