They were not overly aggressive in first few days. Actually, in the North especially, they were trigger and suffered, even by their own admission heavy casualties. I do not know why on Earth they were thinking if they truly believed that Ukraine would surrender in a few days and they'd be welcomed as liberators, especially outside of the Donbass Region.
It is as though Russia learned nothing with regards to the war in Chechnya. They should have had an expectation of urban combat, or even if they do not storm cities, they should have undertaken the sam extent of extensive operations to surround a cities as they did in Grozny.
They should have operated on the worse scenario assumptions and also taken into consideration certain differences between the Chechens and the Ukrainians, these both being respectively that the Ukrainians were determined to fight on the one hand, and the Ukrainians have significantly better AA and Anti tank weaponry that the Chechens did.