You See, I Told You So))) — Andrei Maranov

Sun Tzu, The Art of War:

I-18. All warfare is based on deception.

III-18. Hence the saying: If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.

On point one, from what I can see from where I sit, US and Western strategists were sucked in by Russian deception, failing to see what Russia was actually doing. This continues. Maybe they do understand and are saying something else for deception, in this case information warfare, which the US and UK are winning hands down in the Western media, although at the cost of imposing censorship on alternative media.

On point two, as Andrei Martyanov observes, US leaders do not understand the Russians, and I would add, they do not understand the Chinese either. Scott Ritter shows this in the case of Russia. I say this about China as someone that studied under Chinese martial arts under Chinese masters for decades. This is revealed by surprise rather than anticipation. 

This fault line became abundantly clear to me in the case of Vietnam, for example. The Americans repeated the mistakes of the French and like them were defeated by an apparently inferior force.

The Russian did make two mistakes, however, according to Scott Ritter. First, they underestimated the degree of Nazification of Ukraine in the eight years since Maidan in expecting that ordinary Ukrainians would be happy to be liberated from this menace. That turned out to only be true for the Russian sections in the East. This presents a problem with their major objective of de-Nazifying Ukraine. Now they will likely have to limit this to the hardcore that are fighting in the East.

The second mistake, according to Ritter, is purely political, that is, reducing civilian casualties. Usually, civilian casualties in war run about 1:1 for military and civilian. Russia aimed for much less (and hit their target on this), but at the cost of limiting military efficiency and effectiveness. Ritter points out that this is a "mistake" militarily, but politics supervenes over military objectives, since war is politics by other means (to paraphrase Carl von Clauswitz). 

Ritter's conclusion is that Russia was indeed slowed down in its advance but it did not seriously disrupt the military plan or materially influence the facts on the ground that the Russian military is aiming to create for negotiations. This tying one hand behind the back militarily did not get in the way of degrading the Ukrainian military to the point that maneuver warfare is beyond their capability now strategically and logistically as a result of the superior Russian air power and artillery, including missiles.