“But when [in God’s plan] the proper time had fully come, God sent His Son, born of a woman, born under the [regulations of the] Law, 5 so that He might redeem and liberate those who were under the Law, that we [who believe] might be adopted as sons [as God’s children with all rights as fully grown members of a family].”
The book of Matthew starts off with a genealogy unlike any of the other gospels. It starts us off from Abraham the father of faith all the way to Jesus. This tells us that there was a script and a plan. There were things and people that had to fall in place before Jesus was born. When they all fell in place then it was the fullness of time for God to send his son to be born of a woman.
The book of Ecclesiastes tells us that there is a time and a season for everything. We need to understand that times and seasons are in the hands of God and he is the beginning and the end. He knows everything, the whole story from start to finish, he is all knowledgeable meaning he knows all there is to know and he cannot learn any new thing because he knows it already. He is also all powerful. With all that in mind, he sets things in motion, creating time and placing man under the confines of time and seasons. He alone then knows the right times and seasons for his purposes to come to light.
Looking at Jesus and the mission he came to accomplish, there were things that needed to be in place to facilitate the success of his mission and purposes and bible scholars will tell you that looking at his mission, Christ came at the right time.
In the fullness of time means that from God’s perspective with his purposes at heart, it was the right time. For us we may look at the situation and think it was not, but then again we do not have a complete picture of the past, present and future. He does.