Except then they were being attacked, had the Russian winter on their side, and had conscription and the heavy industry fully mobilised. Plus eventually lots of American-made kit (which wasn’t necessarily better weaponry but at least was made to plan, had spare parts etc).
It took the Russians a while to transition to the great victory in the “great patriotic war”.
Incidentally, this is why I don’t write them off yet, though I sincerely hope Ukraine clocks in a big win. Russians do have the resilience and stubbornness to push through. Whether that can overcome decades of corruption etc remains to be seen.