I am a firm believer that Putin did not send his best soldiers and equipment into the fight. They may have sewed some insignia of such on their uniforms, but they are not trained operators and have old crap for equipment.
Paranoia about the US and NATO made the decision to hold back easy on Putin’s part
Lots of people thought that Russia sent in second line units first. It was a easy to way mentally handle what was happening. The reality is, the Russian army has had severe problems for years.
When fighting in Chechnya, Georgia and Syria it was easy to explain away problems. Now that they are facing a equally capable and determined opponent, their weaknesses are all out in the open.
Why? It makes no logical sense.
It’s not the troops that are important, it’s the tanks and ships. The “arms.”
You can draft people. It takes a while to replace a ship.