Karl Marx thought the lower classes needed to develop class consciousness and a revolutionary party in order to end their oppression. He believed that capitalism was an exploitative system where the working class (proletariat) was exploited by the bourgeoisie, who owned the means of production.
According to Marx, this exploitation could only be ended through a revolution in which the proletariat took control of the means of production and set up a socialist society based on common ownership of wealth.
Marx believed that capitalism would lead to class conflict, which he saw as being between the capitalist class and the working class (the proletariat). He argued that the capitalist class would exploit and oppress the working class, who would eventually rise up and overthrow it. This would lead to a socialist society where there was no private ownership of capital or land, but rather these things were owned by everyone in common.
In addition, Marx thought that workers would be able to unite and overthrow capitalism because they shared a common interest in overthrowing capitalism. He believed that workers were alienated from each other under capitalism, but once they realized how their interests were aligned against those of their bosses, they would come together and establish a socialist society where everyone shared equally in the benefits of wealth creation. He also believed that history was driven by conflict between different classes; therefore, as long as there were classes (rich vs poor), there would be conflict between them.