Mucus Maximum and Rooters.com will of course spin their propaganda, but they don’t know any better than anyone else what is happening - nor do they care. All that matters is cheap SPIN.
What is known - Shoigu is close friends with Putin and is nearly as old as him. Shoigu is one of the most popular public figures in Russia, always serving in the Army and serving whoever is President, but avoiding political pronouncements.
It is also a fact that he is nearly 70 years old, and asked to retire in the past, but given coming war in Ukraine, stayed at his post.
What’s more likely is that jow the war is 2+ years in, showing progress, and Putin has won election for another six years. So he has chosen to retire now.