There has been zero monetary motivation for any Russian actions. The Ukrainian war, even if it was a swift victory, would have been a net loss monetarily. Pirghozin could have kept collecting money and just let his people die.

Wagner fought for money certainly from the government, but still in Russian interest. Thus their honor upheld.

Suggest that you read about the history of the cossacks, it will give much better idea of their mentality. If you played Witcher blood and wine, that was based on the cossacks of Russia/Ukraine.