The answer (I gather) is that while there is indeed some historic disunity between north and south (or north and everywhere else) in Mali, these Islamists (Jihadists?) based in the north are not really of Mali and these outsiders are indeed trying to impose a strict brand of Sharia law that the locals don’t actually want:
Mali has been in crisis since last January, when Tuaregs in northern Mali began a separatist uprising, newly invigorated by an influx of fighters and weapons from Libya after the fall of Col. Muammar el-Qaddafi.
A military coup by junior officers angry at how the government responded to the Tuareg uprising followed in March, leaving the country in disarray and hastening the loss of its northern half to insurgents. Islamist groups, some with links to Al Qaeda, quickly pushed aside the secular Tuareg militants, taking over northern towns and imposing their strict interpretation of Shariah law.
The fighters appeared to find little support among the local population, who said the harsh version of Islam they sought to impose had little resemblance to the moderate faith practiced by most people here.
I admit, I was mostly interested in the video because it had a list of artist names that I could Google. It was only in trying to understand what they were singing about that I started to sort through the finer points of the back story. I appreciate any further insights you can share.