"Socialist" was intentionally introduced in the Preamble by the Constitution (42nd Amendment) Act, 1976. What was its principal aim?

Socialist aims at eliminating inequality in political and religious affairs.

A Socialist Society is a society that's ruled by the working class. The working class would hold power and replace the political, economic and social system established by the bourgeoisie in a Capitalist Society. The State/Government would exist solely to oppress the bourgeoisie.