Why NATO Military Intervention in Ukraine won’t Lead to WWIII

Why have NATO countries not already militarily intervened in Ukraine? The reason is highly effective Russian strategic deterrence. The blatant fear in the West is that Russia will invade the EU, but that is impossible as long as Russian forces are stuck in Ukraine. As long as the Ukraine war goes on the EU is safe, but contrary to perceived opinion would military intervention by NATO countries in Ukraine not risk a further conflagration but would rather be effective in driving out the Russians from Ukraine and thus restore the peace. Russia would be defeated and would have no choice but to join the global American system of alliances in order to encircle China so as to protect Siberia and thus help avoid Chinese WWIV as intended to conquer thinly populated areas around the world and subject them to Han colonization, including parts of North America.