It's just posturing. It can help your negotiating position if your opposite party thinks you're irrational. A pol who's willing to kill his entire family and everyone he knows is a very rare animal indeed. I might believe him if he were career military. Instead, he had a sinecure at the KGB.
Yes I agree just posturing. But I think Putin has overreached. Russia is a thugocracy which is ruled by a bunch of oligarchs. Forget the Kremlin. These guys are being financially hurt by Putin and I will not be surprised if they move him out and somebody else in. Not necessarily kill him but sideline him. The guy is worth about $40 billion so its not like he can’t enjoy the rest of his life with his 31 year old gymnast girlfriend.