Why did congress created the law that allowed 18 year olds to vote?

During debate of the 1970 extension of the Voting Rights Act, Senator Ted Kennedy argued that the Equal Protection Clause of the Fourteenth Amendment allowed Congress to pass national legislation lowering the voting age. ... However, the Court upheld the provision establishing the voting age as 18 in federal elections.

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the treaty of brest-litovsk was a peace treaty signed on 3 march 1918 between the new bolshevik government of russia and the central powers (german empire, austria-hungary, bulgaria, and the ottoman empire), that ended russia's participation in world war i.