Here are two answers that address different parts of the question:

• Why do maps universally have north as up?, with a quotation from an answer by /u/khosikulu followed by /u/khosikulu joining in the discussion in person; answer focusing on Enlightenment-era cartographers choosing to put north at the top
• Why does the North direction almost exclusively get portrayed as the top of maps?, answered by myself; focusing on the reasoning used by the ancient precedent for the choice made in the Modern era (Ptolemy)

So the tl;dr is that Ptolemy made that decision in making his atlas of the world in the 2nd century, because he had most geographical data for the northwest portion of the Africaeurasian landmass and because it made sense to him to put that in the top left corner of the atlas. After Ptolemy and in the Mediaeval period there was no consistent practice. Then in the 15th century cartographers standardised on Ptolemy's practice because Ptolemy was hot stuff.