Why are Paul's writings in the Bible?

[LinuxGal]

Personally, I think whatever Paul meant to say exactly regarding persecuting Christians in his past life, he was exaggerating what he did, to make himself sound like he was the worst of the worst before he became the best of the best. So maybe there is a grain of truth to him having been mean to Christians, but I think this got overblown through his exaggerations and through the beliefs of later Christians

Going by his account in Galatians, the word of his persecution three years prior was already out on the street and needed no embellishment from him.

Galatians 1:22-23 And I was still unknown in person to the churches of Judea that are in Christ. They only were hearing it said, “He who used to persecute us is now preaching the faith he once tried to destroy.”