They don’t need to be recruited, they enthusiastically volunteer
As they did in the 20s and 30s. It is not just that they had socialist professors, it is that they believe that by virtue of their education and their obvious superiority by getting into college they are smarter than anyone else and thus can determine what is best for society and then work to make the world a better place, which always comes down to killing off everyone who opposes their Utopia or who might oppose it. It's for the Children.