Often times regime changers find that taking out the top guy or gal creates more problems than it solves. From Patrick Armstrong at strategic-culture.org:
Moscow knows what Washington has not yet learnt: it’s not just one guy, it’s a whole country and sugar hits don’t last.
Every time – and we’ve just had an illustration – someone in Kiev makes trouble for Russia, the Internet is full of people crying on Putin to just go in and knock them over. A sub-variant of this is that Moscow should have invaded after the Maidan coup, arrested all the nazis and put Yanukovych back to serve out the rest of his term under the now-forgotten agreement hammered out by the EU.
But there’s actually a good reason why Moscow, in Ukraine or earlier in Georgia, did not invade and knock Zelensky or Saakashvili over and why it doesn’t forcefully deal with other irritations. And that reason is a very simple one: it’s not that it couldn’t have done it – there was nothing between Russian power and Tbilisi in 2008 or between it and Kiev in 2021 – but, simply, experience. Both Moscow’s experience and its observation of others’ experiences.