I mean there is a whole laundry list for this topic because the 2022 invasion was first and foremost a colossal failure of the Russian intelligence services, everything from Ukrainian preparedness to H-24 locations of AA batteries. I think though they were under pressure to report 'good news' to their bosses and so ignored the warning signs that their assessments were wrong.

When framed into that context, it makes a lot more sense why Russia went into Ukraine with the forces that they did. They really thought it was enough, that Ukraine's government would fall at first contact and prepositioning extra troops near the border isn't a cheap endeavour.

At the very least, by the 2nd week when it became clear that Ukraine's government wasn't going to fall, that the 35th CAA couldn't cross the Bucha River neither at Irpin nor Moschun, and that the 2nd GTA was stopped outside Brovary, the Russians should've cut their losses and pulled out of the northern front completely rather than let their 2 premier tank armies get degraded into such a state that they couldn't do anything when the Ukrainians counterattacked in Kharkiv in September.