> the Russians are not stupid
these 2 points have been on my mind unrelated to your argument. I do not think they're stupid which is why I can't help to figure out why they botched this up. The whole thing looks like an unhinged ego trip of a single ruler that has grown increasingly isolated (maybe because of the pandemic), like Stalins final days. But Putin isn't Stalin.
So either they failed on strategy, nobody was brave enough to question Gerasimov, or the bigger plan is yet to reveal itself. For now it's Occams razor I think.