There are five pillars of Islam and Jihad isn't one of them. That being said, one of the forms of Jihad is the 'defensive Jihad', which as we can see from history is clearly used as newspeak for an offensive religious conquest. Jihad comes from the historical context of Muhammed's (PBUH) Arabia: a clan-based culture with little resources and literacy as well as immense wealth from the silk road, all of which was centered locally around certain coastal cities. Piracy, blood-fueds, banditry, and eternal wars were the norm as clans/cities fought for clientel and trade routes. In fact, Islamic polygany arose because without it Arabia wouldn't have had a stable population... because there were too few surviving men.
A religion born in war would need certain clauses to justify war, otherwise it wouldn't survive.
In modern times the influence of western culture is seen as a threat to Islam, and so fundamentalist organizations founded in response to the Soviet-Afghan war prey upon weak minded Muslim boys and convince them that wanton murder-suicide will stop the juggernaut march of globohomo. In reality terrorism just galvanizes the west into hating them even more.
And then on top of that, certain petroleum organizations (both globalist and muslim organizations, mind you) profit immensely from a permanently destabilized middle east. The more destabilized an area is, the larger the population of boys to prey on becomes, and the more fundamentalists an area has (terrorists), the more destabilized an area becomes. It's a feedback loop which produces the clusterfuck we have right now.