Well, people did a lot of things. But Crimea is a wholly different thing in that regard, due to no one involved wanting to start an actual WWIII, as well as either having the population of Crimea on its side, or sufficiently suppressing it by force, whichever may truly be the case. More should have been done in my opinion, but Palestine, if fully recognized as a state, could be far more successful in appealing to the UN. Sadly, international law is only as strong as countries are willing to enforce it, which is a shame. Greater powers always get more leeway with such things.