its not out of the question, especially since resistance in its very nature becomes more decentralized and dirty the second the government is weakened or falls.

Take a place like syria, it went from a centralized government to a heap of insurgencies and many sides killing people en-masse.

If anything though, that's Russia's goal. You invade a country you create insurgencies and those insurgencies will be much more evil in character than the government Russia is intentionally destroying.