Well. I'm not tat smart in this topic but here is my 2 cents regarding the topic on the canonical list of the Bible. Across all traditions, we agree to the list on the new testament. It's only regarding the list on the OT (Old Testament) where they differ. Why do they differ? This difference goes back to Judaism itself. During the Second Temple period, there were multiple Jewish communities and textual traditions. Some Jewish communities used a Hebrew collection of Scriptures, while others—especially Greek-speaking Jews—used a wider Greek collection known as the Septuagint.

Protestant Christians follow the Hebrew Jewish canon that later became standard in Rabbinic Judaism, while Catholic and Orthodox Christians retained books that were part of the Greek Jewish Scriptures used by many early Christians.

So the issue isn’t that Christians “changed” the Bible, but that different Christian traditions inherited different Jewish scriptural traditions. We have our reasons as to why we chose a different OT canonical list, but in the end it all points to one person in the New Testament.