I am curious about the Russian strategy as the next guy, but here is what I see.
1. Russia now has 80K regular soldiers, 20-30K Wagner Group, 20-30K Chechens and 40-50 territorial forces in the theater.
2. Russia has far more forces inside Russia and in Belarus.
3. Tens of thousands of regular Russian troops participated in the Far East Exercises.
The forces Russia has in the theater is far too small to obtain a quick victory. They have a cavalier approach to this war. It is as they are fighting an opponent by cutting him with a small pocket knife while carrying a war axe on the back. You only do that if you judge that there is no question of you eventually winning this war. Could they have misjudged the scope of their problem? Given that Putin had a very good record as a leader and he won all the wars that he initiated(Georgia, Chechnya, Syria and Crimea), I highly doubt that he misjudged the situation.
Given the lack of mobilization or even adding the other troops they currently have after the defeat in Kharkov, this is not a careless mistake, it is intentional. When fighting Ukraine, they do not want a quick victory, they want to fight a long drawn out war with relative low intensity.
I don't buy the part about them starting a war that they can't get out of. It is about the survival of Russia and all the internal stakeholders are aligned on it. It was not started haphazardly. Clearly they prepared for it for many years and waited for the right opportunity to do it. They knew that once they start the war, losing would mean the end of at least the Putin regime and likely Russia. Further, they have the means to win the war. They just need to pull the war axe from their back and start to hack away. Also, when faced with unfavorable odds, as in Kharkov, they are more than willing to retreat and accept defeat. This does not look like a group that will carry on if they see the iceberg ahead.
We can reasonably conclude that now, their objective is not to conquer Ukraine. It is likely that Ukraine is not now the main objective as Ukraine does not have agency to abide by treaties it signs.
It is likely that the cost of keeping the war going is not too burdensome. With the current tempo, they can probably continue the war indefinitely.
At this point, I can further speculate on the reason behind the way they fight the war, but rather than risking this being deleted by monitors, I will leave it for you to speculate on your own.