Why were the early Christians especially concerned about protecting and safeguarding the message of Jesus Christ by writing it down?

Answer 1

Well, scholars have worked on this issue for years. The general idea is that the early Christians at first expected the immediate return of Christ. However, when that didn't happen, there was a concern that the stories of those who had been his disciples (the eyewitnesses, as it were) needed to be preserved and passed on to the coming generations. Therefore, they were written down. The extent that they had been codified into standard forms as oral tradition is one of the debates. As they were told and re-told in a group settings, they were put into easily-remembered forms, and it is the story in these forms that were written down.

Answer 2

The Apostle Paul wrote:

Acts 20:29 For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock.

Acts 20:30 Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them.

Acts 20:31 Therefore watch, and remember, that by the space of three years I ceased not to warn every one night and day with tears.

Saint Peter wrote:

2Peter 3:16 As also in all his [Paul's] epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.

2Peter 3:17 Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.

They didn't want believers to be swept away by every "wind of doctrine" (Ephesians 4:14) spouted by the next traveling evangelist who came along. Rather, they wanted the believers to stand fast in the original good news that they were taught (2 Thessalonians 2:15), and to listen critically to whatever was preached in the church to be sure it stood up to close scrutiny (Acts 17:10,11).