Putin does not trust anyone. So he hired a guard of Kadyrov. And as payment for the loyalty to him is given to Moscow. Putin lost the Chechen war.
Putin does not trust anyone because he is very sneaky and expects the same of others. And he bought a Kadyrov puppets.
I don't know how Putin bought Kadyrov but this private army is in Moscow as the hosts. I think that Putin was forced to do so because he's afraid even his