one important fact is; Russia have lots of investments,money and effort in Ukraine like factories, energy units, schools, universities, banks, govt buildings, roads, hospitals and many other things.. if you expect Russians and Putin to say bye bye to this much money , effort and history, I'm afraid you have to wait long
Sevastopol. Access to the Mediterranean and the western seas. Russia will never let that go. Ever.
yep.. thats the most critical fact that Russians solved at the blink of an eye..
Russia likes to play being the friend but then takes advantage of any situation that comes along, like the political turmoil in Kiev. A bit like a so called friend stealing your wallet while you are unconscious after a road accident.

But in this case they didn't find any cash just an IOU for $6bn to pay every year.

It is the same with industry in East Ukraine, their only market is Russia, where they are still churning out Soviet era quality of goods that have no market in any Western country, they will have been better off letting the west having to pay the subsidies, rather than Russia, who will also be facing a hostile majority of the population, who they will have to buy off or fight off.
As Professor Mark Galeotti an expert on modern Russian has said is that Russia had an agreement for the base in Crimea until 2042 at very little cost per year. With Yanukovych he had a president who practically had 'Kremin' tattooed on his forehead, but because he was so determined to stop him signing the EU free trade agreement, he has now lost him. What Putin is doing makes no logical sense, his emotion over EU agreement has got the better of him. In return for his invasion of Crimea he is gaining nothing that he didn't already have.
With sanctions and other restrictions with Western countries, who will now only deal with him because they have to, not because they want to, he will have gained popularity at home for a bit, but at a much bigger long term cost.