I think your analysis here is correct. The massively outnumbered heroes at Mariupol tied down enough Russian forces for long enough to ensure Russian defeat in the north of Ukraine. So then for political/propaganda purposes, i.e. to save face, they had to advance in the Donbass at any cost, so eventually taking Severodonetsk and Lysychansk was a huge drain on their forces - it was not smart fighting. Now it looks like they are crumbling on all fronts.
I now expect either the internal ousting of Putin, or an attempt at salvaging the war through a full mobilisation of all military age males in Russia, by Christmas.
