Why does Daesh always succeed in stimulating people’s evil side?

Terrorism is no longer an organizational structure with clear-cut disciplines. It has become an affiliation of evil; people from all over the world come together to express their anger and hatred by committing terrorist acts. Daesh has successfully expanded its terrorist activity across the globe simply by capitalizing on the dark side of human nature and inciting people to attack innocent citizens. Why has Daesh succeeded in spreading hatred while the entire world has failed to prevent its crimes or to curtail its efforts?
The recent attack on innocent civilians in New York by a Muslim Uzbek immigrant led American President Donald Trump to re-stress his immigration policy of barring citizens of several Muslim-majority countries from entering the US. Upon learning that the Uzbek terrorist had come to the US after being randomly selected by the “Diversity Visa Lottery Program,” Trump also said lately that he wanted to terminate the program. Will Trump’s policies prevent terrorism in America?
Terrorism is on the increase, despite substantial advances in security measures worldwide. The reason is that a segment of society that is living among us firmly believes that terrorism is a moral act, that by massacring innocent citizens they can recover their missing rights or to release their anger. 
We keep thinking of new methods and tools for preventing terrorist activity; meanwhile, however, terrorist attacks in Western nations have shifted from complicated operations to simple ones — all it takes is to invoke cowardly people to attack a random group of innocent civilians. 
Actually,  Trump’s proposed policy of preventing large segments of Muslims from entering the US will provoke more terrorist attacks. The threat that the US (along with many other nations) is confronting comes from some angry, hate-filled residents who would like to get their revenge on society, or from external terrorist groups who disagree with US foreign policy and work on inciting those residents.
“God is great,” the phrase shouted by the Uzbek terrorist, is no longer a novel terrorist statement; it has become a hackneyed slogan, repeated by large numbers of terrorists. 
Nevertheless, it is still the most appealing label that the media is happy to highlight — and it gives terrorists the satisfaction of imagining that they are abiding by their religious beliefs, bolstering their hope of entering paradise! In truth, these terrorists are too ignorant to comprehend that, in essence, the fundamental principles of Islam condemn violence.
Billions of universal citizens certainly believe that the world is an unfair place. If we assume that a tiny percentage of these explicitly endorse the principle of “an eye for an eye,” we can easily conclude that a few million believe that terrorist attacks are justifiable. It is easy to see that, out of this tiny percentage, there will emerge numbers of weak, sick-minded citizens who could eventually engage in terrorist activity.
Many nations have anti-terrorism divisions that are often a part of law-enforcement departments. They work to dismantle terrorist organizations and to identify potential terrorists — but they don’t have the ability to shape their societies and to persuade citizens to condemn terrorism. 
Furthermore, although it is clearly a universal threat, many nations tend to denounce terrorism less strongly when it is not happening on their soil. Sadly, the debate about who is a terrorist and who has a legitimate cause to fight against enemies has not been settled yet.     
We live in an era where hatred has by far overcome kindness. The 9/11 “why do they hate us?” question needs to be revised into, “how can we better diffuse their hatred?” We need to work on directing people to express their hatred in ways other than engaging in terrorist activities. It is the responsibility of governments and societies to identify both tense issues and aggravated people and to work on mitigating and softening them. 
Meanwhile, western nations need to think intelligently of new means and methods that can bring about a significant reduction in terrorism — beyond the physical measures that currently dominate their minds and are reflected in their policies.