While a reliance on local amateurs has allowed the Islamic State to announce that it can stage terrorism around the world, it has also led to many failed attacks.Instead of opening fire on a church, Mr. Ghlam shot himself in the leg. Instead of laying waste to a music festival this past summer, the Islamic State recruit in Germany detonated his bomb prematurely, killing only himself.The same thing happened the day before the end of Ramadan on July 2 inside a police compound in Indonesia, where another remotely guided attacker hit the switch on his crudely assembled suicide vest.“He didn’t even knock over the flowerpot on the ledge next to where he blew himself up,” said Sidney Jones, director of the Institute for Policy Analysis of Conflict.Indonesian officials say that the suicide bomber had been incited to attack by Bahrun Naim, a 33-year-old Indonesian man who is now one of the Islamic State’s most prolific cyberplanners, operating from the group’s capital in Raqqa, Syria.Initially, Mr. Naim wired money to families in Indonesia to pay for travel to Syria, officials said. Later, the bank transfers he sent were to be used to buy the chemicals needed to build explosives, according to the interrogation records of his recruits.In just over a year, the young men he was in contact with attempted at least six attacks, targeting a police post, a Buddhist temple and a church, as well as foreigners visiting the country. In November, a college dropout who the police said had at least been initially in contact with Mr. Naim was arrested as he prepared to attack the embassy of Myanmar. In his home, the police recovered a quantity of explosives that could have resulted in a blast twice as powerful as the 2002 Bali bombing, which killed 202 people, the police spokesman told local news media.Yet nearly all of the plots attributed to Mr. Naim have failed. And it was human error that finally led to the arrest of Amriki’s followers in Hyderabad.The plot began to unravel in June after the men were instructed to collect a 10-kilogram bag of ammonium nitrate left beside a canal next to mile marker No. 9 on the Vijayawada Highway.They returned to Mr. Mohammed’s home to begin preparing a bomb, but could not figure out how to replicate the steps in the instructional YouTube video sent to them by the handler. “We could not succeed in making powder, as it became jellylike paste,” Mr. Yazdani lamented, according to the transcript of his interrogation.They tried using a tea strainer. They tried heating it longer. They began talking on their cellphones about their efforts to “cook the rice.”By then, the police were wiretapping their calls and suspected that all the food talk was a crude attempt at misdirection. Early on June 29, the police banged on the door of Mr. Mohammed’s home.In his bedroom, they found the half-cooked explosive in his refrigerator.