At the end of the cold war Russia and US gradually reduced the armaments facing each other in Europe to the extent that war was not a realistic possibility. But then Ukraine started to want more western freedoms and strategically important Crimea was annexed. Then further moves towards the West caused Russia to feel insecure and Ukraine was invaded, it was a half hearted campaign, neither side had the weaponry to fight a war with any determination.
That has now changed Russian has much more capability and NATO is still rationing arms supply to Ukraine, furthermore, sanctions on Russia has proved totally ineffective. They are receiving help from many other countries that need their oil and others that need their armaments.
If only Ukraine had stayed neutral it could all have been different, focus is on Gaza currently that will change soon enough when full scale fighting in Ukraine starts again.