Evidently the plan is working. Here's an excerpt from the article:
Three years after ISIL(Islamic State in Iraq and the Levant) surprised a lot of people, especially the Iraqis by quickly seizing Mosul in mid-2014 American intel analysts believe that attacks against key ISIL personnel since then played a major and largely unreported role in the defeat of ISIL. These attacks became more frequent and more effective as ISIL lost most of its territory in Syria and Iraq.The article goes on to explain how these people are targeted and is pretty interesting. The problem with crushing ISIL, however, is that it's like striking liquid mercury with a hammer - the blow scatters it into numerous globules that run all over the place. Thus, as ISIL suffers ever greater losses of territory cells of terrorists are popping up all over Europe.
This gave key people fewer places to hide and even more importantly forced them to move more frequently and often without the careful planning and preparation they had learned was essential for survival. By early 2017 the impact of the damage was pretty obvious.
While the hunt for the senior leadership got the most publicity, these men, especially ISIL founder and leader Abu Bakr al Baghdadi, were not the most important target (unless the goal was headlines and maximum media audiences). The key to crippling ISIL as an organization were those leaders responsible for finance, logistics and media.
These were harder to replace and the senior ISIL leaders knew that success at raising huge amounts of cash (mainly via looting and smuggling, but also extortion and ransoms paid to free kidnapping victims and slaves) and maintaining effective communications for the finance and recruiting operations were more important. The logistics included obtaining weapons and explosives and moving them to where they would be most effective.
For example a number of attacks carried out in the months before Mosul fell (and Raqqa was surrounded) in July led to the loss of several key people who managed and ran the ISIL media networks. This included Internet distribution of propaganda and ISIL documents as well as the ISIL Amaq News Agency.
Attacks against these media networks have been going on for nearly three years although the results were often kept secret (short or long term) in order to exploit the confusion these losses created within ISIL. ISIL would often deny accurate reports of their key people dying or being captured in order to maintain morale.
The hope is, presumably, that once ISIL is completely defeated on the battlefield, the allure of an inevitable caliphate will evaporate and Islamists will find it harder to recruit volunteers for suicide missions for what will seem to be a lost cause.
At least that's the hope, but unless the U.S. and its allies start waging a war of ideas in which the weapons are public arguments made by moderate Muslims against extremist readings of the Koran there will always be a pool of disaffected young men eager to inject meaning into their lives by martyring themselves for what they believe to be the will of Allah.