Why are there so many languages when the origin is one?

Allah knows best. Your Lord is the Most Wise, All-Knowing. We do not have any certain knowledge of the wisdom behind that, but we know that our Lord is Most Wise, All-Knowing. He, may He be glorified and exalted, says (interpretation of the meaning):

“Certainly your Lord is Most Wise, All-Knowing”

[al-An ‘aam 6:83]

“And Allah is Ever All-Knowing, Most Wise”

[an-Nisa’ 4:11]. 

By His great wisdom, He made many languages and made people of different colours, as He, may He be glorified and exalted, says (interpretation of the meaning):

“And among His Signs is the creation of the heavens and the earth, and the difference of your languages and colours”

[ar-Room 30:22]. 

The reason may be so as to highlight His almighty power, for He, may He be glorified, is able to make one language for some people and another language for others, for this is more indicative of great power. 

There may be other reasons for it of which we are unaware and that we cannot comprehend, but scholars other than us may understand them. 

The point is that one of the clearest reasons behind it is that He, may He be glorified and exalted, is able to do all things, therefore He gave people many languages and told us that this is one of His signs (interpretation of the meaning): “And among His Signs is the creation of the heavens and the earth, and the difference of your languages and colours” [ar-Room 30:22]. 

Just as He made them of many colours, including red, black and white, and shades in between, and He has caused them to vary in size, so that some are tall and some are short, and some are in between, and He has caused you to vary in attitude and intellect, the same also applies to the issue of languages. All of that is indicative of His almighty power and highlights the fact that He does whatever He wills, may He be glorified and exalted, and there may be other great reasons behind that which we do not understand. End quote. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him).