Moses wrote it, or rather took dictation from God and wrote all down.
Many, though not all people who call themselves Christians, believe these books are God-breathed and true and for our edification and education, even though we are not Jews, as they teach us about our own history and are instructions to us from God.
Of course Christians must know Torah. How else do we learn the perfect standard Jesus Christ (Yeshua HaMashiach) lived and taught, which reveals we are sinners and need of His spotless sacrifice. When Peter said we must walk in Jesus foot prints, he was referring to God’s standards. We find those standards not only in the NT but as Christ said:
Luke 24:44-49 NASB
Now He said to them, “These are My words which I spoke to you while I was still with you, that all things which are written about Me in the Law of Moses and the Prophets and the Psalms must be fulfilled.” Then He opened their minds to understand the Scriptures, and He said to them, “Thus it is written, that the Christ would suffer and rise again from the dead the third day, and that repentance for forgiveness of sins would be proclaimed in His name to all the nations, beginning from Jerusalem. You are witnesses of these things. And behold, I am sending forth the promise of My Father upon you; but you are to stay in the city until you are clothed with power from on high.”