I would have to conclude that there was a lot of tension between some of the Jews and Gentiles in the early Christian church. Paul is at such pains to chastise both Jew and Gentile equally in the early chapters of the book of Romans that there must have been some politics at work.
There had been no apostle at Rome by the time this letter was written, no central figure around whom they could rally, and it is likely that the five or more small house churches in Rome were at least a little divided.
Never having been to Rome, Paul has to lay some groundwork for his gospel.
Ronald L. Dart
Ronald L. Dart (1934–2016) — People around the world have come to appreciate his easy style, non-combative approach to explaining the Bible, and the personal, almost one-on-one method of explaining what’s going on in the world in the light of the Bible. After retiring from teaching and church administration in 1995 he started Christian Educational Ministries and the Born to Win radio program.