Verse 1 indicates that this response arrived “soon.” It is a response to the second letter, not the first. Pahoran does not explicitly mention the first letter, and it is possible, given the circumstances he relates in this letter, that he did not receive it.
What is important for this letter is that he did receive it, and that he didn’t spend much time getting a response back to Moroni. Of course, we cannot know how long “soon” was, but given the slow nature of communications as well as the political unrest, it was certainly a longer time than modern readers would expect of something that happened “soon after.”