I attracted a good answer. It turns out that after Ukraine changed sides with their revolution in 2014, Russia was afraid for their control of the black sea from Sevastopol and that’s why they invaded the Crimea in 2014. That is possibly why they started the invasion, so they could gain a strip of land to sustain their activity there in Sevastopol.
That’s a good question. These strategic things always seem very arbitrary to me.
But in this case I can imagine a big cartoonish radar working better from Sevastopol. Worth a war tho?