Question

Why was the Supreme Court's decision in Wesberry v. Sanders important?

Answer 1

It reduced the impact of rural/urban population differences in selecting State Representatives to Congress. This took (abused) voting power of urban centers away.

Explanation:

"The complaint alleged that appellants were deprived of the full benefit of their right to vote"
"...no matter what the mechanics of an election, whether statewide or by districts, it was population which was to be the basis of the Hose of Representatives."
https://www.law.cornell.edu/supremecourt/text/376/1