Why didn't the Russian army not do its mission in Ukraine as it should?

We all see that Ukraine didn't fall in 96 hours. And the question is why that thing is happening. During the exercises, the operations are done well. But the flop is happening in the real mission. All Russian units including the famous Spetsnaz are not what they should be. So what is the problem? There are many possibilities for that kind of surprise.

One of them is what the Russian army didn't expect. Is that the Javelin missiles will be so effective. And the Russian military experts expected that they could shoot down Ukrainian drones and fighters down easily by using their most modern jet fighters. 

The other version is that the troops are not prepared for their mission. There is the possibility that the commandos didn't get vial information like what their target looks like. If the team's target is a command center they should know what that thing looks like. And of course, they must know where is the point where they should put the explosives. 

That lack of information can contain the scenario where paratroopers don't even know, that they are going to battle. This means that the leaders of those units just forget to tell them that there is a war where they are going. Or maybe some of those troops believed that Ukraine was surrendering. So they didn't expect what they will face. 

There is always the possibility that there were only the best teams in the exercise and the skills of regular teams are far lower than in those "show teams".  There is also the possibility that the commanders are not telling truth about their strike capacity. There is the possibility that some "old guys" are not done their exercises as they should. And of course, if we think that failure is not acceptable in those exercises and demonstrations. 

There is also the possibility that some commanders are used fraud in those pieces of training. That means that if the commander put the detonators or explosives on the targets and then launches them at the right moment that thing makes the effect that looks like a successful artillery strike. There is always some reason for the flops in real situations. 

Of course, things like foodservice are one of the most fatal things in combat missions. When military men are in the combat zone they need ammo supply but also food and something to drink. If there is no food the sugar level in the blood will decrease. And that thing makes operations very hard.