Wasn’t that an opinion that was shared by many back then - that a full invasion would be way too costly with little to gain and Russia is just sabre-rattling?

Wasn’t that an opinion that was shared by many back then - that a full invasion would be way too costly with little to gain and Russia is just sabre-rattling? Most people in Europe could not imagine a full out war and considered the warnings from the US as merge fear mongering.