Too many parents shut down the 'Why?' question asked by every young child.
Why would Russia put mobile anti-air in Crimea?
Ask the question, and the answer will be obvious. They plan to defend themselves. Or they plan to advance. Either way, they are expecting a fight.
Are they just posturing so they can avoid a fight with Ukraine over Crimea? No - that is not how the Russian mind works, and certainly not regarding Ukraine - the wayward teenager of Mother Russia who momma probably plans to turn over her knee.
Here's the link.