Neither one of them , or all the others who take a somewhat similar position, are absolving Putin from his primary responsibility of being responsible for this war.
Should we summarily dismiss all opinions which in some fashion give some justification for Putin's position? Don't think so. Chomsky there was talking generally re major power relationships. Kupchan put in more the way most all other experts see it. i think. There would be differences of course but i think saying in looking at Putin's position on Ukraine consider the U.S. and the Cuba.n missile crisis is fair.
""It’s true that Moscow’s dismay at the prospect of Ukraine’s membership in NATO most likely is fed in part by nostalgia for the geopolitical heft of the Soviet days, Mr. Putin’s paranoia about a “color revolution” arising in Russia, and mystical delusions about unbreakable civilizational links between Russia and Ukraine. But it is also true that the West erred in dismissing Russia’s legitimate security concerns about NATO setting up shop on the other side of its 1,000-mile-plus border with Ukraine""
I don't see Chomsky in that in any manner justifying Putin's war against Ukraine.
It was Plato who said, “He, O men, is the wisest, who like Socrates, knows that his wisdom is in truth worth nothing”