Understanding jihadi groups

I finally found, courtesy of the good old Beeb, a reasonably convincing attempt at explaining the rationale behind the Islamic State (IS, aka ISIS or ISIL, depending on the day of the week) and their apparent disregard of Islam in favour of shock-and-awe tactics of extreme violence, something that has always puzzled me.
Even al-Qaeda made some attempt, albeit somewhat feeble, to justify their crimes on a theological basis. IS, the unruly and vicious offspring of al-Qaeda, has never done so and is completely unapologetic. Rather than try and justify their actions according to the precepts of Islam, their approach is just to get the job done, as effectively as possible and with no recriminations, using whatever means seem to be effective. By stressing brutality and barbarism, IS is banking on attracting recruits through intimidation, and through its image of unapologetic single-mindedness. For them death, torture, even genocide, is its own justification. And it has been remarkably successful in attracting recruits, both at home and in the Western world, particularly disaffected youth who feel they have nothing else to lose.
The "job", as IS sees it, is also much narrower than that of al-Qaeda. Although it wants ultimately to establish a Sunni Muslim caliphate across the whole world, it sees the first step towards that goal as the removal of the local Shia Muslim infidels (it looks on Shias as infidels, just as Westerners are). Only then can it concern itself with the rest of the world.
The only other movement that is even comparable to IS is Boko Haram in northern Nigeria (see the essential BBC guide to this mob). The name Boko Haram can be roughly translated as "Western education is forbidden", but this is just one of the planks of their belief. The group's official name is Jama'atu Ahlis Sunna Lidda'awati wal-Jihad, which means "People Committed to the Propagation of the Prophet's Teachings and Jihad", and it too is trying to establish a strict Islamic state or caliphate in the region, in place of the political entity of Nigeria, which it does not recognize.
Their approach seems to be roughly similar to that of IS (although the two groups are not officially linked in any way): use whatever means and violence is deemed necessary to get the job done, political optics and theological rationale be damned. Increasingly, in recent months, Boko Haram seems to have begun mimicking IS and their tactics and pronouncements, although the mass kidnappings of schoolgirls remains their trademark action.
Although IS seems to receive more media attention, and their inflammatory video set pieces (the beheadings, the burnings, etc) are apparently deliberately designed with that purpose in mind, the recent numbers of victims are remarkably similar. According to NBC, there were some 10,340 IS-related violent deaths in the last year (measured in this case November 2013 to November 2014), and 10,733 Boko Haram-related deaths.
A different report by the BBC compares the deaths from jihadism in a single month (November 2014), which shows significantly more activity by IS than Boko Haram in that particular month, but also serves to remind us that there are other jihadist massacres still going on in Afghanistan (courtesy of the Taliban), Somalia (al-Shabaab) and Yemen (AQAP, or al-Qaeda in the Arabian Peninsula), where the deaths of hundreds of people receive little or no media coverage.
The estimable Guardian was one of the few media outlets to ask why Boko Haram's victims receive so much less attention than those of IS (and independent IS-wannabe attacks like those in Paris, Ottawa and Quebec). However, other than the lack of Western journalists on the ground in Nigeria and a generalized claim that African lives are perhaps less newsworthy than Western ones, convincing reasons seem hard to find. Certainly, the various efforts of IS, and even more so those of self-radicalized individuals, pale into insignificance against the immensity of some of Boko Haram's raids, one of which, at the beginning of January 2015, may have resulted in the deaths of 2,000 people.
So, do I understand jihadism any better now? Not really...