The answer, lies in Ukraine’s geostrategic value to the EU and the grand Russian dream of Mr. Putin.
Sea Trade and politics
The total seaborne trade is the region is minimal about 2.5% of global trade. But Russia and the Ukraine alone handle over 75% of this trade. The Ukraine is clearly the largest country with its ports at Odessa, Mariupol, Illichivsk, Mykolaiv, Izmail. Russia on the other hand depends mostly on Novorosiysk for access to the black sea.