Why did the people who wrote it write it?

Did God want it to be written?

1 Because they wanted to appear wise/superior.
2. Because they didn’t want men chasing their wives.
3. Because they wanted youth to show respect.
4. Because they wanted to scare their daughters into remaining virgins.
5. Because they wanted any man who deflowered his daughter to have to marry her.
6. Because they wanted others to share their values and support them by stoning those that didn’t.
7. Because they wanted control.
8. etc.

No

There are very different explanations between the NT and OT. I've examined the NT more than the OT so I'll speak to that. A recent podcast from Stand to Reason discussing this book:

https://secure2.convio.net/str/site/...u2sjg2.app202a

with one of the authors has some insights into this.

Jesus appointed the apostles to evangelize, found churches, and then to follow through with instruction for those churches. So during the 1st century the apostles represented and delivered God's Word, mostly orally, but also through writings. As the apostles died off, their authority was transferred to those documents recognized by the church as either written by an apostle or closely associated with one - i.e., written by a companion and/or approved by apostles.

So the NT was formed and recognized largely in the 1st and 2nd centuries and mostly universally accepted as authoritative, long before Nicea. The purposes of the documents were first to give an account of Christ - His life, ministry, death and resurrection, then to provide basic instruction in what the gospel was about and how God had changed covenants, what it means for both individuals and the church, replacing Israel with the church, and finally, to make some prophecies about the future.

The purposes are mostly the same as they were for the OT, just very different subject matter.

Here's what Luke has to say about it.

Luke 1: 1-4 Many have undertaken to draw up an account of the things that have been fulfilled among us, just as they were handed down to us by those who from the first were eyewitnesses and servants of the word. Therefore, since I myself have carefully investigated everything from the beginning, it seemed good also to me to write an orderly account for you, most excellent Theophilus, so that you may know the certainty of the things you have been taught

The simple recap:

1. Apostles wrote about Jesus because they were instructed to by Jesus (and they believed Jesus was Son of God).
2. Jesus (so, God) wanted it to be written.

Thanks NR and Jerok.