We have been programmed to Doubt it. It's obvious by your comments that your opinions have been influenced greatly by other things, & other spiritual sources. If anyone doesn't believe the Bible's testimony of itself - they are disbelieving God, they are questioning the words of Jesus, Apostle Paul , and Peter and John etc .
Imo, because I know from the change in me, before and after, if a person doesn't know the Bible is the literal God-breathed inerrant authoritative word , they only know of the Son, they don't know Him personally.
The problem is there are many who hold so tightly to their own beliefs, opinions and preconceived definitions and that they do not approach the Bible with earnestness,as God's one and only Authoritative source, but in holding their own opinions as hallowed and inerrant instead, they subject the Bible to their own wills. It is apparent in the handling of the Bible scripture, who are submitted & lead by the Holy Spirit and who have been lead by their intellect or other "movements",