They were setting the table for this for several years. Russia asked for evidence they were in violation and the US could not provide any even as Russia offered hard evidence the US in violation with their deploying anti-missile systems which the US claimed to be used against Iran.
Even an idiot could see deploying such systems to Poland was hardly going to intercept something from Iran.
That comment from the US diplomat to NATO indicating the US would launch a preemptive attack on Russia to take these systems out was very clearly setting THIS latest announcement up.
Pepe Escobar has an exccellent take on this. Little of this has to do with National Security. What it has to do with is eliminating competition to US Corporations. The US wants Europe to buy US Natural Gas and Russia and China are threatening the stranglehold that Europe and the US have on several key industries. As example Russia has developed a new aircraft jet engine that is being put into commercial airliners and is a direct threat to Boeing and Airbus.
The US is trying to reindustrialize after allowing much of their industries to set up shop overseas and in order to do that they have to eliminate the competition for that industry. Forget “National security”. This is about the 1 percent wanting MORE. They are getting it domestically by demanding cuts to Social Spending programs and they are getting it abroad by having the USA and allies eliminate Governments that are restricting access to resources the Western Powers think theirs by rights and by trying to ensure Russian and Chinese industry is locked out of various markets for their goods.
Rest assured some guy in some think tank pointed out that after ww2 the US dominated the world industrially. They pointed out the reason for that was that any competition had been eliminated due to the war and the destruction it visited on other Countries. In “making America great again” they are trying to re-create that situation on the ground and will do so even if it means a world at war again.