Did Mr. al-Baghdadi put a succession plan in place? There are highly credible rumors that he did.

But even if there was no concrete plan for succession, ISIS had already returned to its terrorist roots, with the capacity to inspire attacks all over the globe. Even after losing its territory, ISIS continued to attract adherents.

But more important, we need to remember that the world is fighting not a single man, nor even a single organization, but a movement. Unfortunately, many of the risk factors for the rise of ISIS still remain. Among these are weak states with poor governance, unemployed or underemployed youth, simmering sectarian tensions or civil war.

ISIS exploited many of these factors to spread its “provinces” into other nations wracked by conflict, among them Afghanistan, Libya, Nigeria and Yemen. Many of its provinces remain in place. Despite losing what remained of its caliphate in March, ISIS still managed to carry out several major terrorist strikes, including in Sri Lanka, Afghanistan and Iraq.

For those of us in the West, ISIS exploited social media to attract and inspire global followers, in what became known as “open-source jihad.” Unfortunately, this is one of a number of lessons that other terrorist groups will take on board: Until social-media companies find a way to address the dangers of anonymity online, terrorist groups and criminal rings will continue to follow suit.

On Sunday morning, President Trump provided an unusual level of detail about the workings of the mission to take Mr. al-Baghdadi down. Still, in the coming weeks and months, we may learn about how global intelligence personnel penetrated ISIS, and the kinds of international cooperation that led to his demise.

But one thing is already clear: This was not the work of a single president or a single nation taken over a single week. It involved the courageous citizens of the “deep state,” those often-nameless intelligence and military personnel so dedicated to protecting the lives of fellow citizens that they are willing risk their own. It also, according to Mr. Trump, involved cooperation from Russia, Syria, Iraq and Turkey — as well as intelligence from the very Kurds that Mr. Trump abandoned when he pulled American troops out of northern Syria.

In this regard, Mr. al-Baghdadi’s most significant mistake may have been to make himself the enemy of the entire world, inciting his enemies to work together against him.