The resurrection is a proposition of fact. It's either true or false.
Marxism is a theory. It's a conjecture that the world would be much better if X, Y, and Z; and that thus-and-such explains history, and so on.
True believers in theories die for those theories all the time. They don't die knowing those theories are false; they believe them to be true.
However, if the resurrection is a falsehood and the apostles knew it (and were not deceived), they died for something they knew to be a lie. Sane men don't do that. So either they were all very skillfully deceived, or they were insane, or they were telling the truth and the resurrection is a fact.
Good point.