The crux of Marxism is that capitalism has solved scarcity (essentially, poverty), and that any resultant scarcity isn’t a reflection of material constraints (such as tradeoffs between risk and return, or the choice between various types of products, which might arguably not be ‘material’), but rather the decision of a small group of people to artificially restrict the quantity produced, thereby increasing the price of the product. Additionally, the excess/supernormal profits from these artificially inflated prices would be retained by the owners of the industrial equipment rather than shared with workers (because that would incentivise more workers to work for you, increasing the amount you produce, decreasing the price you can sell for).
If you accept this message, then you have a putative explanation for why the world is divided into rich and poor (the “natural” result of conflict between workers and owners, with the owners seemingly winning), and prescriptions on what to do about it (eliminate ownership as a concept, thereby eliminating this conflict).
It’s appealing for all the usual reasons. It’s pretty simplistic, so you can preach to a large number of people quickly, especially those who aren’t likely to critically analyse what you’re preaching. Its very simplistic explanations lead to very straightforward prescriptions, abolish property through any means necessary. It creates an outgroup an easily identifiable villain to channel your frustrations towards, your bosses and their bosses. It taps into pre-existing animosity, because the people who dislike their bosses are more susceptible to being converted.
Latest Answers