Seems that some of the Bible’s credibility lies in the fact that it does not just tell us what we might expect to hear.
For instance, both testaments describe in detail the weaknesses and failures of the people whose story they tell (i.e. leaders of Israel and the disciples of Jesus). Historians view potentially embarrassing reports of ones own group as an indicator of authenticity.
Why would the nation of Israel, or the church of Christ retain a body of literature that catalogs their personal and collective moral, social, and spiritual failures?
By present day standards, many would see such admissions as being unpatriotic and damaging to national interests (for Israel), and unfriendly to the collective reputation (of the church).