I had assumed that Matthew was probably writing from Jerusalem. But
it appears that, for several reasons, the gospel of Matthew may have been written
See this article.
If that is the case then there is even more reason to suspect that Paul himself may have commissioned, or at least encouraged, the synoptic gospels to be written for his churches.
Luke and Mark were close associates of Paul, of course. But if Matthew was in Paul's base church that could explain why he also contributed to this written record of the life and teachings of Jesus Christ.