The first reason for Jesus’ Birth was mention by St Mark the Apostle.
"The Son of Man came not to be served but to serve and to give his life as a ransom for many." (Mark 10:45)
Why do we need a ransom?
We need a ransom to be paid in exchange for our redemption because we have sold ourselves into sin and have been alienated from the Holy God.
When Jesus gave up His life as a ransom, our slave-masters: sin and death and the devil, were forced to give up their claim on us. As a result, we were allowed to be adopted by God again and be again members of God’s family.
In his letter to (Galatians 4:4–5 ), St Paul the apostle says, "When the time had fully come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law so that we might receive adoption as sons."
In other words this redemption or this ransom sets us free and hence enables to become a member of God's family. We had run away and sold ourselves into slavery. But God was born and willingly paid a ransom and redeemed us out of slavery and taken us into the Father's House.
To do that, God's Son had to become a human being so that he could suffer and die instead of us to pay the ransom.
That is the meaning of Christmas.
In the letter to the ( Hebrews 2:14 ), the writer says, "Since the children share in flesh and blood, he himself likewise partook of the same nature that through death he might destroy him who has the power of death."
In other words, Christ took on human flesh so that he could die and by His death, He would pay a ransom and set us all free from the power of death.
Again. Why did Jesus come? Was His only reason to pay this ransom?