Which circumstance prompted the adoption of the 23rd amendment

Basically, people in the District of Columbia weren't consider a state so they didn't have any electoral votes to give, which meant that the people who lived their couldn't vote. The 23rd amendment gave them electors and allowed people to vote even though they are not a state or recognized as such.

People didn't like that their vote didn't count, that they couldn't vote for who would represent them.