It's easy to see why they spin it this way if you watch at least one program of Vremya or similar Russian "news" or read Putin's article on Ukraine from last year. They don't consider Ukraine a 'real' country, and Ukrainians as normal people. The supremacism, bigotry and entitlement to Ukraine is mind blowing, and unfortunately quite a number of Russians agree.
So it will always be the West's fault, or an accident but they will never admit to a defeat by Ukrainians as it will challenge their supremacist views. I expect next they will claim that it wasn't a Neptun missile, but maybe a British Harpoon, or why not even a CIA sabotage operation. And they cannot help themselves not to provoke and draw in Western countries that wouldn't care less about Eastern Europe.
This type of thinking is already playing out on Russian TV where the failure of Russia to capture Kiev in three days is explained by Western arms and training even they were already known before the declaration of the "Special Military Operation".
It gives me hope that supremacists, bigots and bullies lose because they underestimate their opponents.