NATO went too far with deploying anti-ICBM systems right next to Russia's border (with the Ukraine conflict being the most obvious result of this strategy) essentially nullifying their ability to strike back in case of war. So now they have to find a new way to deliver their weapons, with our missile shield in place, be it cruize missiles or something else, and this is escalating the new cold war.
I don't like seeing research in nuclear weapons done by anyone, especially Russia, but I can't help but feel like this one is on NATO and not Russia.