While everyone is obsessed with Iran and Israel I would like to draw the attention of those who care to the following article in The Guardian:
Shia rebels seize Yemen's third largest city, say military | World news | The Guardian
In a nutshell, Yemen treads in the steps of Afghanistan, Iraq, Syria and Libya. Revolutions in all of the above mentioned countries started as secular protests against authoritarian regimes. The outcomes are well-known to general public. What some of us consider unpredictable side-effects others attribute to Pentagon's direct interests. Controlled chaos absorbs whole countries, letting American concerns shine through smoke and blood.
The map of the Mediterranean sea oil routes should give you a hint:
Everything has a reason to happen.