Unlike the Taliban, I don't really see true governance as a goal of theirs. They don't have, nor are they likely to win the support of local populations; one reason why fear through massacres and brutality is now one of their main tactics. The Taliban always had a more solid ideological core and really drew a lot of its recruits from religious schools in Pakistan in a way that Boko Haram has been unable to do so. More importantly, Boko Haram (due in part to their brutality) hasn't been able to forge the strong links to other Islamist groups that the Taliban depended on (the Haqqani Network). I think we definitely did see ideological drift in the Taliban, as we tend to see in all long term militant organizations, but not to this extent save for more recently (particularly Pakistan's TTP faction). Some factions do have those links, particularly to AQIM, but those aren't the ones under Shekau.