As an atheist, I believe that the religion is wrong and comes from the culture. So saying that the culture/religion is responsible for the disparity in terrorism is easy. Something about the culture and its interaction with its religion is leading to this. If we are to believe people can do good in the name of Islam, we can also believe they could do bad.
Islam is not the only source of terrorism, but it is unique in the type of terrorism and the volume it produces. Like I said before, there is a lot going on, but just looking at the data something is unique about Islam aka its culture.
In another thread people talked about how Islam has grown more conservative over the last several decades. The question being: why?
After thinking about it, I think it's an issue of no moderating force in Sunni Islam.
If we compare Islam to a nuclear reactor, the Quran is nuclear fuel and without carbon control rods, you will eventually get a runaway chain reaction and a Daesh-like meltdown.
The Ottomans kept a lid on the crazier parts of their Empire; the Ottomans were analogous to control rods.
With the Ottomans out of the picture, the cultural center for Islam reverted to Saudi Arabia--the Land of the Two Holy Mosques. The Saudi family came to power with the help of the crazy-conservative Wahhabis, who were pissed off at the royals allowing various things like US military bases on Arabian soil, education for females, and 1000 other things having to do with modernity. The royals did not want civil war, so they basically bribed the Wahhabi clerics with vast amounts of money to build mosques all over the world to preach the Wahhabi hard line.
What we're seeing today is the result of decades of oil-fueled Wahhabi hate speech spread to every corner of the world, with no country willing or able to fill the role of the old Ottoman Empire to moderate the nuclear chain reaction.
There's no easy fix to this problem, but one thing we can do is to accelerate alternative energy to decrease the funding source for the Wahhabis.