Putin is interested in the Crimea for the port of Sevastopol. His interests in the Ukraine are fleeting if at all. Further, I could not care less about alleged protests in support of the Ukraine in Russia. We have protests in the US for various things that are all crap as well. Russia has taken very few aggressive steps towards the Ukraine that can not be militarily linked as protection for the Crimea and the Russian troops staged there. If Putin had wanted the Ukraine, the flag of the Russian Federation would be flying over parlaiment from day 1. NATO would have been powerless to stop it. The ripple effect thereafter would have been a mess and Vlad probably would have lost if NATO countered, but he has little to no interest in the Ukraine so there he sits until the political landscape stabilizes.
I just don’t see taking over the rest of Ukraine as being worth the trouble for Putin. Now his main concern is that Ukraine doesn’t join NATO.