Name three people who were instrumental in the development of communism

Three people who were responsible for the development of Communism were Marx, Engels and Lenin.

Explanation:

Karl Marx and Frederick Engels were two thinkers who were responsible for the idealistic backdrop of the communist thought.

Their two books, Das Capital and the Communist Manifesto were responsible for the societal change and the ideological shift towards communism that happened in the late 19th century.

Then, Lenin was the first person to run a communist government thereby giving it a practical establishment and his take of Communism was thus the one being followed.