It's not annexed. There are troops, part of the Russian 14th army, there. (IIRC, they were formed locally and petitioned to be made part of the Russian army. There are officially Russian peacekeepers there--mostly to stop fighting, since the Moldovans had so little stomach for fighting that they decided to let the independence movement, such as it was, get established and rooted and take over. This was the Ukrainian scenario. Unless you are willing to fight for something, it's not really all that important to you. The Belarus president, Lukashenko, pointed this out in exquisite irony: If Crimea was that important, part of Ukraine, why wasn't a shot fired to keep it. He said that he'd fight for every inch of Belorus. If the Ukrainians had done this early in the Donbas, the problem might have been solved by law enforcement--before the buildings were taken and armed seized, militias organized, crates of weapons imported.)
Which is Putin's point. If you are willing to take what you want and nobody does more than spout rhetoric at you, you get what you want. The strong man with a will to power succeeds; the decadent Western wimp mumbles in futility and is beaten.
China's watching. It's already set up an oil rig and kicked out neighoring countries' ships from part of the S. China Sea. We're teaching China the same lesson. Because we're afraid that if we stand up to a bully we might get involved in all-out war.
People want a multipolar world. There's one of the poles.