Why is Russia going after the Crimea? It's just a hostile acquisition
As I've said for years, Russia is an energy company with all the trappings of nation-state — John McCain recently paraphrased me by calling Russia “a gas station masquerading as a country.”
Everything Russia does militarily is aimed at expanding it's energy interests. From acquiring new oil and gas basins to exploit to forcing countries to allow it to build new pipelines or expand old ones. It's also used everything from extortion to cyberattack to pull it off.
Here's a map of the natural gas basins in Ukraine. Note the big one under the Sea of Azov.