Why some many monarchies in alternate history post 1950s

For unfathomable reasons many timelines with a POD in the 20th century (post 1950s) or after a Nuclear War many countries or surviving states have monarchies. What is the reasoning for choosing as a writing plot for example that a nuked France or Germany becomes a monarchy? whatever former republics become a ragtag of small kingdoms, duchies, etc? For example 1983DD? Any ideas of why this happens.