Why did the Corinthians write to Paul?

The Corinthians wrote to Paul because their congregation was divided and troubled. They had problems over leaders like Peter and Apollos, moral problems, and relationship problems within the church family. So they sent a letter asking how to handle these matters and what they should do.

Les explains that the whole letter of Corinthians deals with a series of problems. The Corinthians had come to the apostle in the form of a letter asking, "Well, how do we do this? How do we handle that?" Some in the congregation said they listened only to Peter, others to Apollos, and such things divided the little congregation. They also had moral problems and problems of relationship within the church family. Paul had to defend his apostleship because some called him a fake or imposter, claiming Peter had authority since he walked with Jesus for three years.

Why did the Corinthians write to Paul, and what does the whole letter of Corinthians deal with?

The Corinthian congregation wrote to Paul about a series of problems—divisions, moral failures, and relational conflicts within the church family—asking how they should handle such matters. The whole letter of Corinthians deals with those issues while Paul also defends his apostleship against critics who claimed he lacked authority.