That’s because Russia has a strong interest in nominally retaining Crimea as part of Ukraine. From the disintegration of the Soviet Union onward, Crimea, with its traditionally separatist leanings, was always a destabilizing factor. It served as a direct avenue of Russian pressure on Ukraine, and also guaranteed almost a million “pro-Russian” votes in Ukrainian elections, ensuring the dominance of the pro-Russian eastern half of the country over the nationalist western half. If the Ukrainian nationalists had been smarter and more farsighted, they themselves would have advocated a renunciation of claims to Crimea in order to remove this needle in...