If properly handled maternity cover is a pretty painless process. It's not like a boss quitting: there are handover periods and keep-in-touch mechanisms. The new manager should be explicitly hired for maternity cover, and have their expectations set. It happens in most of Europe, almost without comment it's so routine.

If it's a massive career-impacting hassle for employees of people on leave at Amazon, where they "suffer significantly" that's yet more evidence for Amazon being a terrible place to work.