Russia was in economic doldrums following the Soviet collapse and was a pitiful giant that seemed in danger of breaking up. Russia was forced to make peace on the only terms on offer at the time.
Twenty years later, Moscow scents its moment, treaties and international guarantees be damned. Crimea was simply too good a moving target to relinquish forever.
It was Russia's "Treaty of Versailles"....and we all know what the original led to.