God allows man to make choices and exercise free will but God is ultimately in control. 

Yesterday we read about the flood, where God wiped out humanity because of their great evil.  Noah and his family were spared and the world began to repopulate.  in Genesis 9:1, God told Noah, “Be fruitful and multiply and fill the earth.”

As the population multiplied, however, the people began to congregate together and did not follow God's instructions to spread out and fill the earth. They also began to unify in their plans to glorify themselves and be self sufficient.  “Then they said, “Come, let us build ourselves a city and a tower with its top in the heavens, and let us make a name for ourselves, lest we be dispersed over the face of the whole earth.”” (v4)

The people spoke one language which unified them but not to glorify God.  They did not trust that God would bless them if they dispersed as he had commanded.  Instead, they wanted to remain together finding their comfort and security from each other. Not only were they disobedient but they were full of pride and arrogance, wanting to build something with their own hands that would bring glory to man and disregard God. 

God intervened in a drastic way to promote the disbursement of the people. “Come, let us go down and there confuse their language, so that they may not understand one another’s speech.” So the Lord dispersed them from there over the face of all the earth, and they left off building the city.” (v7-8). God allows man to exercise free will but He does not leave the impact of man's evil intentions to go unchecked. 

Men  became separated by location, language and culture.  God, however, ultimately wants man to be unified in Christ.  None of these barriers have stopped the spread of Christianity throughout the world.