Because this isn't the intended strategy, but rather then resultant strategy.
Modern Russia seems to suffer from the same weaknesses as the USSR: garbage-in, garbage-out. If you staff an entire bureaucracy (including your military command structure) with Yes-Men, you get "Yes" responses.
When the question is "Are we prepared for the invasion?"
When the question is "Will we be able to supply our ground forces?"
When the question is "Will we be able to achieve air superiority rapidly?"
And because that's how hierarchies work, you believe the "Yes" you hear. And make your strategic plans on the basis of it being true.
Consequently, Russia appears to have built an entire invasion plan on a not-insignificant number of lies about their own forces, as communicated by their own mid-level leadership.
Imho, that explains things pretty simply and fully.