Ukraine has a long history of being conquered by surrounding nations. The word Ukraine is actually derived from a Russian word that means borderland. The past ~20 years, after breaking away from the Soviet nation and declaring its independence, has been the longest period of Ukrainian autonomy to date. The last attempt at independence was at the end of World War I, during the Russian Civil War. Ukraine declared itself independent after being conquered by the Germans, and liberated by the Russians. But later it was absorbed into the Soviet Union, which ended its bid for independence. Since the USSR fell, Ukraine has had difficulty forming a national identity. It is heavily economically dependent on Russia, but the Ukrainian elections have swung policies back and forth, away from and toward Russia, causing economic problems. This has had the effect more than once in the past 10 years of inciting revolutionary activities from the Russian interested east and south and from the European leaning west.
Putin is obviously not being truthful about his actions or the reasons for them. He initially denied any military action in Crimea. He later claimed he was only protecting Russian interests when he took over the Crimean military bases. The speech after the annexation showed that he felt Russia had a right to claim the territory. He later admitted that the Russian military was behind the whole story from the beginning. What is he really up to?
My theory for the reasons behind all of the recent Russian military activity are as follows.
First, historically, Russian rulers have been remembered by how they contributed to the growing empire, or despised by how they lost territory and/or power. And Putin isn't getting any younger. So he is thinking about his legacy.
Second, Russia's source of power lately has been its riches in natural resources. The centrally owned and operated natural gas monopoly Gazprom has proven to be a valuable commodity and weapon.
Lastly, both Crimea and the Donets Basin are resource rich regions. The sea surrounding Crimea is a natural gas gold mine, and the Donets Basin has always been a valuable coal mining community.
A result of the last Ukrainian revolution (when Yanukovich was forced out of office early this year) was Russia realizing the opportunity was ripe for gaining (back) some valuable territory. The interim government is weak. So it makes perfect sense to take advantage of this situation. Nevermind that this is all completely illegal. So was the transition of power after the Euromaidan revolution.
Many people in the Donets Basin are fine with becoming independent or joining Russia, just like Crimea was. Others want to remain Ukrainian, but they are a minority. I get the sense that the feelings aren't too strong either way, (except from the protestors themselves) because the people understand that their lives won't change too much for the better or worse no matter which side of the border they end up on.
The recent call by Russian and Ukrainian authorities for the protestors to disarm themselves leads me to optimism. However, Putin is not taking military action off the table. He still is waiting for an excuse to "liberate" the area from the west.
I have to commend the Ukrainians for the relative calm that persists among the people not participating in the revolution and the protests. Waiting for people to calm down is a much better reaction that fighting against them. People are controlling crowds of protestors in Kiev by telling them that chaos is exactly what Putin wants, and they calm down. The unrest exists only as small pockets, while the rest of the country tries to get on with life as best they can.