What caused removal of literacy test?

The removal of literacy tests as a prerequisite for voting in the United States was primarily a result of the Voting Rights Act of 1965. While literacy tests had been used for decades, often to disenfranchise Black voters and other minority groups, the Act explicitly outlawed their use and other discriminatory voting practices. The Act's passage was directly spurred by the Civil Rights Movement and the persistent struggle for racial equality. The blatant discriminatory application of these tests, along with other tactics like poll taxes and grandfather clauses, finally became untenable in the face of increasing national attention and legal challenges.