As indicated by the word "this" in the sentence, the answer is in the sentences before.
Marx knew very well that capitalism, by its nature, fosters social isolation, leaving "no other nexus between man and man than naked self-interest, than callous cash payment." This creates passivity in the face of personal crises, from factory layoffs to home foreclosures.
He suggests that capitalism causes people to be selfish & therefore isolated. This he says causes people to accept everything that happens in a passive way. That is, do nothing but accept crises, such as factory closures.