Who were the Judaizers that the Galatians were starting to believe instead of Paul?
The Judaizers were false teachers who came into the Galatian congregations demanding circumcision and law keeping. They opposed Paul's pure Gospel of Grace, troubled the believers, and perverted the Gospel of Christ, drawing them away from the grace of Christ into another gospel.
Les explains that the Galatians were beginning to believe these Judaizers who were coming in and demanding circumcision and law keeping, as over against Paul's pure Gospel of Grace. They were slipping into the influence of another Gospel, which was not another but a perversion. Les notes that when Paul was absent, false teachers came in like ravening wolves and tore the little congregations apart. These perverters troubled them and would pervert the Gospel of Christ. Paul also wrote to Timothy that all in Asia, including Galatia, had turned against him.