Catholics and Orthodox claim apostolic succession. Basically, the idea is that their branch’s leadership has revealed the correct interpretations of the Bible in the centuries after Christ’s ministry, and that their branch’s leadership’s doctrinal authority goes back to the apostles.
As a protestant, I reject their claims. But the canon wasn’t formed until long after the apostles died. So how can we trust the canon without trusting the doctrines formed by people in the same chain of succession?