I agree that that period was an outlier in terms of large-scale activism post-WW2. However, there was also the small matter of 50,000 dead draftees in Vietnam that propelled public anger. The US government had a vested interest in making policy changes that kept the peace, especially with the threat of an expansionist USSR on the horizon.

You are getting the dates badly wrong. Voting rights act was 1965, opposition to the war was limited until Tet Offensive.