A black foreign diplomant appears in a major trade city comes and thinks his culture is better?

You mean this guy:

Mansa Musa, also known as Musa I of Mali, was the ninth Mansa (emperor) of the Mali Empire, ruling from around 1312 to 1337. Musa was born around 1280 and died around 1337.

he is best remembered for his extravagant pilgrimage to Mecca in 1324, which included a caravan of around 60,000 people and an immense amount of gold, significantly affecting the economy of Egypt due to his generous spending and gift-giving.

So what is he doing in 1403 Bohemia, 66 years after he died?

Or is he just a fictional character with the same name? If there's no historical basis for the character, then he doesn't have a place in a game aiming for historical accuracy.