I'm wondering if the staging is meant for a two-stage attack.
1. Roll over Ukraine in a blitzkrieg attack, grab the whole country.
2. Roll past Ukraine just a little bit with air power and missile strikes into neighboring states to enforce the message.
The chance of it blowing up beyond that bigly is high, and grave if so. Russia may be slow-rolling this because they expected less defense of Ukraine than is now being pledged.
As someone else mentioned I am beginning to think that maybe the Belarus drills are due to the support the Ukraine was getting. Maybe now Putin realizes he has to take the whole country and quickly. Maybe before he was just thinking take a chunk but now that would leave part of Ukraine that would get an incredible amount of military support from the West right on Russias border. Any strike outside of the Ukraine and we are instantly in full blown WW3. I think even France and Germany would wake up at that point. But who knows? I am just happy when I wake up in the morning and my power and internet still work.