Why did the Corinthian believers still have so many problems instead of being spiritually mature?
The Corinthian believers still had many problems because Corinth was saturated with paganism and gross immorality, and they had only recently come out of that pagan background. As a small newly gathered group, they could not instantly become spiritual giants; their many questions and issues reflected that recent, steeped-in-the-world condition.
Les explains that Corinth was a city just saturated in paganism, with the gross immorality that went with it. The believers were so steeped in the things of the world that even after Paul garnered this little group, they were not a huge megachurch; probably a few dozen at most. These men and women had just recently come out of such a pagan background, so it stands to reason they did not all of a sudden become spiritual giants. They had a lot of problems. Les also points out that the Corinthian congregation actually sent Paul a letter with a whole series of questions, and he answers them one by one. In chapter 1, many were lifting Paul up as the only man to listen to.