It is scary, and the precedent in the world is not for long-term national stability. Even setting aside invasion and occupation, dynasties end, governments fall, and a country’s name might be among its only bits of continuity to the past.
Betting on a country maintaining a continuous government for a hundred years is taking the long odds. Those odds become even worse if the government is relatively new. The USSR lasted less than 70 years, and the current Russian government has only been around a bit over 30(less, if you’d argue that Putin has fundamentally changed it). Stability is truly a bad bet for them in particular.
And they have a giant arsenal of weapons, nuclear and otherwise. “Worrying “ is a fully reasonable response.