The same reason He "permits" his followers to sin.
Not the same as "permitting" his church to teach error. He gave to the Apostles the full deposit of faith and it did not contain any errors. This deposit of faith has been preserved, protected and taught since the day of Pentecost.
We all have free will and can choose to obey or disobey. However, there are consequences to disobeying.
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So then would you allow that from that same reason you speak of, He would also allow the authors of the Bible to transcribe erroneously what the Holy Spirit had inspired within them?