Marx believed that capitalism would cause alienation. In capitalism, the laborer is forced to labor for someone else who is mostly stealing their profit and hard work. This causes the labor to become external from the worker. If the worker was producing for their own means, this separation would not occur.
The worker is then forced to buy products that they have produced. The big company owners exploit the laborers and the general public with this method.

Capitalism Causes Alienation

"Capitalism will self destruct."