When a war ends without the politics being settled, the seed of conflict remains.

However, most either people lack this longer term vision and falsely perceive a physical wins as an ultimate "victory", or don't care because they won't be around then.

"This isn't a peace, it's a twenty year truce!" - Ferdinand Foch, regarding the Treaty of Versailles

As an aside, the U.S's failure to predict the Collapse of the USSR was probably their greatest intelligence failure, with the consequence being Russia beginning a hurtling into the Abyss, arrested by Putin, and a partial reversal of the Democratic trend of Gorbachev. I don't think Demonizing Putin is really going to be helpful. Ignorance of the historical circumstances of Russia brought him in power is analogous to the belief that a Utopian Democracy could simply be imposed on Iraq from above. Take a Spherical Cow in a Vacuum, add some Democracy...