Let me give you the historical play by play.
1) Viktor Yanukovych was removed with 328 votes by the Parliament. The Ukrainian Constitution requires 338 votes and a review of the "Supreme Court". Yanukovych was accused of using snipers to kill protestors but even head members of the EU and Foreign Minsters doesn't buy that. Another source.
2) On February 26th Ukrainian and Russian (Crimeans) clashed in Simferopol over the proposed repeal of Law of Languages by the Ukrainian Parliament. The repeal would have made the Ukrainian the only legal language despite the fact that regional languages were recognized for decades, even in Soviet Russia. There are places in Ukraine where only Hungarian is spoken for official purposes on the local level. Same with Romanian.
3) After this clash the local Russians in Crimea asked Russia to come into protect them because they didn't trust the new Illegal Government of Ukraine and for good reason as I'll explain later.
4) Russian send a small protection force. Considering how many troops are located in that part of Russia.
5) Crimea officially declares a vote.
Russia sending a protection force in to Crimea is typically the status quo when dealing with outbreaks of violence in European countries. NATO sent forces to the Balkans and provide protection to this day. Certain countries declared independence early and fought a bitter war over it. Kosovo on the other hand relied on NATO protection and "declared" independence a good 9 years into NATO control. US and others had no problem accepting.
Crimea was always Russian, just Ukrainian in name. Many in Crimea were mad when Khrushchev gave Crimea to Ukraine symbolically in 1954 as a 300 year anniversary gift. And they were mad when they were forced into Ukraine in 1991/1992. Crimea is and will always be Russian. Crimea wants to be apart of Russia and always has. This isn't news to those who know the history.