The very word Renaissance was coined by a bunch of Italian artists and writers patting each other on the back because they believed themselves very clever (the precise attribution belongs to Giorgio Vasari, who wrote about it in his 1550 book, Le vite de' più eccellenti pittori, scultori, e architettori or "Lives of the Most Excellent Painters, Sculptors, and Architectureists [sic]").

The fact of the matter is that Italy hit a balance of power in the late 14th/early 15th century: fighting between the Italian polities stopped and the upper classes were able indulge in patronage of the arts. Italy had always been the economic center of Europe since the days of the Roman Empire, and Arab texts had been flowing into Italy since the eleventh century, the causes of the artistic boom post 14th century are much deeper than any one thing. This hasn't stopped many theories being put forth purporting to have found the "Cause of the Renaissance" (the Black Plague's reduction of population levels and the consequential increase in salaries is consistently popular, however I've also seen the "Fall of Costantinople" fairly often) I think it really couldn't have happened anywhere else.

All kinds of scholars, not just artists, came to Italy from from all over the west and brought the ideas of the Renaissance home with them. When they took hold Northern Europe, you have the "Northern Renaissance," helped by the increase in disposable income brought about by the boom in Atlantic trade after the turn of the 15th century.