In brief, lingua francas originated and developed through contact and accommodation in villages, city- states, and nations. They spread through the exchanges among people within a community, the episodes of colonialization by small family groups, or the occasional flights of a whole community from overpopulation or disaster. Most of the lingua francas in human history can trace their origins back as languages of commerce and trade. Some began as pidgins, progressing on to becoming creoles and later vernaculars and national languages in their own right. Some have faded away. Those that have remained have adapted themselves well to contexts of change in their encounters with new speakers of the language.
Andi Jaihutan Silitonga (Fri,) studied this question.