The job of the historian is often to pull together broad themes and trends, then give them a snappy title that people will easily recognise and understand. That’s how we end up with labels like “The decline and fall of the Roman Empire” or “The Rise of Hitler and the Third Reich”.
When I first read about this, the story was in the non-mainstream press and was confusing. What was not clear was the agenda. Most referred to the organisation as the Islamic State of Iraq & Syria but then used both ISIS and ISIL as the acronym for this. Why ISIL? Shortly afterwards, Islamic State of Iraq & the Levant appeared which covered a much wider area than originally mentioned. Could this simply be the early stages of the news breaking as disparate sources slowly pieced the picture together from differing fragments of the whole picture?