Ukraine broke the Minsk agreements, and Russia recognized that the agreements weren't worth anything then. Pretty clear-cut. Russia's economy is being strengthened not just by temporary wartime economics, but also by being further embedded in Chinese trade, as well as increased cooperation with the global south. Russia's desire for the four oblasts has been consistent, and they have been steadily gaining territory month over month as war in Ukraine becomes increasingly unpopular.

You have proven nothing regarding the war being about "vainglory" or "mass expansion," these are absurdities one must conjure out of thin-air in order to treat Russia not as a country of humans but instead as a saturday morning cartoon villian. This is Marvel-movie style analysis of complex geopolitical interactions.