While I agree with most of the answers already provided, I think a simpler explanation is in order. It is this: In light of the failure of the world's people at that time to populate the entire world as God wanted--and commanded--them to, God had to enforce his command through extraordinary means.
So God created mankind in his own image,
in the image of God he created them;
male and female he created them.
God blessed them and said to them, “Be fruitful and increase in
number; fill the earth and subdue it (Genesis 1:27-28a NIV, my bolding).
In other words, God's plan from the beginning was for the entire world to be populated by his image bearers. When the people of Babel contravened His decreed will, God in his infinite wisdom scattered them by confusing their languages. They became, you could say, the first diaspora.
The Lord Jesus also gave a similar command to his disciples just prior to his ascension to heaven after his resurrection. We call it the "Great Commission":
“All authority in heaven and on earth has been given to me. Therefore
go and make disciples of all nations, baptizing them in the name of
the Father and of the Son and of the Holy Spirit, and teaching them to
obey everything I have commanded you. And surely I am with you always,
to the very end of the age” (Matthew 28, excerpts, vss 18-20 NIV, my bolding).
No one on the face of the earth is exempt from God's gracious call. Every people group (Gk., ta ethne) is invited by God to repent, believe, be saved, and become a disciple of His one and only Son. The scope of salvation history is universal, for all people, for all time. For Jesus's disciples then, or for his disciples today, to refuse to preach the gospel would be analogous to the people who built the Tower of Babel refusing to fill the earth.