PARIS — Why isn't the Arab world more mobilized against ISIS? The question is genuine, and it might put the finger on the hidden causes that have been fuelling the repeated success of radical Islamism over the past 25 years.

Strategy experts are asking themselves whether U.S. President Barack Obama is doing too much or not enough in the fight against the jihadist terrorist group. Some are surprized by the fact that the U.S. President has not yet ordered airstrikes against ISIS strongholds in Syria, as it has in Iraq. Obama is weak, or so they think. And when they comment on the military aid provided by European Union countries to the Iraqi Kurds, who are on the frontline against ISIS "black shirts," they say that the EU took too much time to react.

To be sure, ISIS has captured Western journalists. Its henchmen executed two American reporters on video. Yes, ISIS has recruited hundreds of young Europeans, who once they return to their countries will be the devoted agents of a jihad against "Jews and Crusaders."

But let's not forget that the first target of ISIS is the Arab world. The jihadists' stated ambition is to reinstate a single caliphate where the most backward interpretation of Islam will prevail, to be preached by Salafis, the advance men of Sunni extremism.

Its enemies are the borders of nation-states. It already managed to largely erase the one between Syria and Iraq, thus carving with the most barbaric violence its first swath of territory for the upcoming caliphate. Lebanon and Jordan could soon become the next targets, and after that, the Persian Gulf kingdoms and emirates.

And yet, it is American planes that are backing the Kurds and what is left of the Iraqi army in their fight against ISIS, while Europe provides the weapons and the "advisers" that always come with it to the Kurdish peshmergas.

This doesn't mean that the armies of the Arab world are incapable and that their arsenals are empty. Far from it. Shashank Joshi, a senior research fellow of the Royal United Services Institute, recently noted in the Financial Timesthat among them, the six nations of the Gulf Cooperation Council possess more than 600 combat-capable aircraft. Meanwhile, signs of some of the most formidable air forces in the world are nowhere to be seen in the Iraqi skies.

Arab countries have historically had few qualms about warring against each other. In the 1960s, Egypt's air force bombed Yemen with chemical weapons. Only a few weeks ago, the United Arab Emirates, backed by Cairo, sent their fighter jets to Libya to tip the scales in the country's ongoing civil war.

Why, therefore, are these same states so feeble in their commitment against ISIS? Why the restraint, or even indulgence, in the face of such a dangerous enemy? You could argue that it is by force of habit, addicted as they are to the regional American police service, since 1945. Like Europe, the Arab world is more than ever reliant on the American military umbrella.

Nightmare scenario

But the real cause goes deeper. It lies in the strategic and religious conflict that is tearing up the Middle East. On one side are Islam's minorities, mostly the Shia, under Iran's protection. On the other are the majority Sunni Muslims, who are accustomed to dominating the Arab stage.

The latter, led by Saudi Arabia, believe — not without some reason — that the Islamic Republic of Iran and its local allies (Iraq's Shia and Syria's Alawites) want to steal the region's leadership from them.

In short, the fight that comes first in the list of priorities of the Sunni Arab world is that against the Shia. And in that fight, anything goes, including fomenting an extremist Sunni movement. In their battle against the Shia, Islam's majorities have fueled Sunni extremism.

Enemy No. 1 for many Arabs: Iran's Supreme Leader Ayatollah Khamenei (sajed.ir)

"For the Arabs of the Gulf, the idea of an Iranian hegemony is a nightmare," French professor Gilles Kepel recently told Le Monde. And this is also true in Ankara. "The Turkish, Qatari and Saudis saw in ISIS the lever that would enable them to get rid of Bashar al-Assad, Iran's ally. The monster they created now frightens them."

It frightens them also because it looks like them. Saudi Arabia practices, nurtures and exports a version of Sunni Islam of which the Salafi-jihadist model, that of ISIS, is merely an outgrowth on steroids.

"For five decades, Saudi Arabia has been the official sponsor of Sunni Salafism across the globe," Ed Husain from the Council on Foreign Relations recently write in The New York Times. Its school books, universities and foundations have been spreading the poison of an Islam intolerant of all other religions and obsessed with the literal application of sharia. ISIS stages the execution of its prisoners while Saudi Arabia beheads them in public.

The monster thus created by the Saudis and a few others worries them all the more since it holds a certain power of seduction among their own population. Attacking it too conspicuously is a risky option. What’s more, almost 1,000 Saudis are fighting in ISIS ranks. The "Arab streets" are receptive to the jihadists' message, a fatal attraction that the Arab regimes fight openly at their peril.