Just as we should not ignore the one time it did work. Was the objective the same in each of the ones you cite and was the leadership the same. Are we o.k. letting Russia have Ukraine--what about Finland, they haven't joined Nato yet.
This possibly could happen via sniper, but internally, Putin has spend years organizing against a coup, especially from the military. He has set up 4 different agencies ( FSB, GRU, SUR, FPS ) and his long time friend Zolotov is the head of all four. The FPS is like our Secret Service, only we have approx 5000 in that agency and he has approx 20,000 in the FPS. He has also openly made sure everyone in these agencies know there are "friends" in each agency who will tell him if someone is considering organizing a coup.
And as stated above--Putin gone --now what !! I have a strong distaste for Putin and would love to see him and Zolotov disappear, but like Cheesehead, if it happen, I would be holding my breath while waiting to see if his replacement The reason it worked one time was due to numerous social, economic, and societal reasons is sane, or at the very least any better than Putin.