Why did God show longsuffering to Paul first?
God showed longsuffering to Paul first because Paul was to serve as the Apostle of the Gentiles and the pattern for future believers. Since Paul was the chief of sinners, God extended mercy and grace to him first, demonstrating longsuffering so that all who afterward believe on Christ might have life everlasting.
Les explains that Paul identified himself as the chief of sinners—not the worst, but at the head of the line—and because he was to play the role of the Apostle of the Gentiles, God extended mercy and grace to him first. This showed forth longsuffering as a pattern, so that everything else would fall into place for those who would hereafter believe on Jesus Christ and by believing have life everlasting. Les also notes that Paul constantly defended his apostleship, that he was the one who brought the Gospel to the Gentiles, and that the mysteries were revealed to him.