you like to carry comments to the extreme...of course they didn't write the old testament, however, when they wrote the bible as we know it, they included the old testament for your perusal.
they did, however, write the new testament. Using "raw material", booke, papers, teachings, tradition etc., they compiled, after much study and discussion, the new testament as we know it today. Was the Holy Spirit involved...well duhhhh, that's where the guidance and the inspiration comes from. With the Holy Spirit, the Catholic church gave the world the bible as we know it. People have since tried to modify what the church presented, but to no avail.....the Catholic Bible is true, complete, and final....any and all changes made to it are in error...all of them.
And yet they screwed it up beyong recognition.