GOOD QUESTION: 
On a wide range of issues, the long tail of East Bloc Cold War propaganda has much more of a foothold in American politics, both left and even more surprisingly, right (I’m looking at you, Tucker Carlson), than it ever had during the Cold War.
Two reasons come to mind, though they are at best partial explanations. One is our elite universities, which have long been home to domestic radicals, but now also house a large contingent of Third World Communists and Islamists, such as Mamdani’s father. A second is the popularity of Bernie Sanders, who had a long career as a Communist fellow traveler before pretending to moderate to become a Vermont senator, and whose increasingly radical rhetoric on everything from greedy bankers to “Palestine” is right out of the wrong side of the Cold War playbook.