Answer:
As Marx's and Engels' ideas were meant for workers and low-income people from various backgrounds, the language they used was simple and clear, so it could be understood widely.
It is also written in a passionate manner expressing strong ideas that are supposed to awake emotional reaction and make the proletariat unite.
Step-by-step explanation:
The intended audience for the Communist Manifesto was the workers, called proletariat by Marx and Engels. They were the ones who are supposed to understand the ideas and react to the poor treatment of themselves, conducted by the bourgeoisie.
That is why Marx and Engles presented their ideas in the manifesto which is not too long, very clear and calls for action.
Their ideas were supposed to reach various people of many backgrounds and to awake their emotional reactions. Marx and Engles used simple and brief language, but the passionate one. They needed to express their ideas strongly, underlining the support for the oppressed, and emphasizing the importance of the rebellion in order to make people believe their intentions and unite.