There's method in Iaroslav's madness. Thing is, there's also probably madness in his method. :P
It's a huge symbolic deal for Bohdan to make it clear he controls the Crimea. Historically (and even today, to a large degree) the Crimea was far and away majority ethnic Russian, with some Tatars. In fact, the Crimea was considered part of Russia until 1954, when the USSR lumped it in with Ukraine for ease of administration. When Ukraine got independence, they made some political deals with Russia and kept it. Still, Bohdan's not gonna have many friends there.