Putin is so far up his own ass he’s ignoring sound military doctrine just for the chance to showboat.
The smartest thing Russia could do right now is effectively freeze their offensive actions, form a hard defensive border, focus on beefing up their supply lines, and use the winter as a shield. And fall back from untenable positions when Ukrainian advances get to strong.
It would slow things down greatly, and they would likely lose some territory but by the time winter comes around they’d be in a much stronger position to renew offensive operations.
But Putin has backed himself into a corner and seems totally unwilling to pursue any sort of formal pause nor defensive posture.