(1) Donbas - though Russia was not initially attempting to annex this area. The negotiations scrapped by the West would have left these regions as something like special administrative regions under Ukraine, akin to what Russia had already been trying to relatively peacefully achieve for a decade with the Minsk accords.

(2) Coal + industrialization + peasants seeking a better life.

(3) Actually quite a lot happened, but I assume you're referencing the fact that a small number of Russian forces were deployed to Crimea. A practical issue when territory "peacefully" changes hands is deterring the former "owners" from simply coming in and trying to kill everybody to immediately reclaim it. The important issue is whether those forces drove coercion or otherwise manipulated the outcome of the referendum in a way outside the will of the people. This is what the West tried to prove, but they instead ended up proving the exact opposite! Incidentally, a comparable referendum held in Donbas was likely outside the will of the people, and consequently - Russia did not recognize it.