I wholeheartedly agree with you - the current war is the result of decades of mistrust, hostility and grandstanding, from both sides of the conflict (NATO and Russia). It is the worse of all possible outcomes, and puts us closer than ever to direct war between these two major nuclear powers.

Assuming we didn't get there though, I think the only part of the calculation that you are missing is that the war is not a horror for Putin and his entourage, and neither for NATO leaders. It is a horror for the people of Ukraine, their army, and the Russian soldiers who actually have to fight it. The seeds of hatred will also prove to be a horror for the ordinary Russians who will suffer greatly in retaliation.

Unfortunately, their leaders and ours will have probably been long dead after content, peaceful lives, uncaring of the harm they have caused.