This is my theory (disclaimer: I have no clue what I’m talking about). They don’t want to show all their cards to the West.
Everything from land forces, to the navy, to the air force, to the intelligence, to the propaganda unit is performing poorly.
And the West has exhibited superior intelligence and PR by all means. The Ukrainian army is much better trained and organized than expected (probably some Western help in their training, or just the psychological hardening caused by the conflict from 2014), and the population is 100% hostile to the invasion.