Trying to make Marxism, which most people are ignorant about, as equivalent to multiculturalism or political correctness, which large swaths of the population dislike, is just a way to slander Marxism. Like claiming Nazism is socialism when there was nothing socialist about the Nazi party after 1920, except its name, which Hitler kept to fool the German people.

Multiculturalism was something devised by European capitalists after WWII. The capitalists were short of cheap labor after the carnage of the war. They started importing foreign labor. There were two lies involved with this. The first, aimed at the local population, was that the immigrants would make their money and go home. The second one was aimed at immigrants. It has come to be called multiculturalism. It was easier to get these people to immigrate to Europe by telling them they didn't have to change anything, that they could keep their language, their religion (usually Islam), their culture, their marriage traditions etc, that they didn't have to assimilate, that they could move to Europe, but live as though they hadn't moved. So many of them moved, brought their families, had kids, made a lot of money for European capitalists but generally remained a foreign enclave. Nothing to do with Marxism. It's a capitalist scheme.