That's true, when workers are not aligned with each others, some get confused who is actually on your side vs against you, and frequently they believe the upper-class will protect them and provide them with support and wealth. I don't think I even have to share examples of how this works out in practice, yet for every revolution it keeps happening with the same results more or less.
You are fighting the upper-class, while some of the working-class people are mislead to fight on the other side. Slowly but surely they'll realize where to go, but often the promises of wealth and what not gets to strong for the individuals to at least try to move up.