One subject that constantly comes up in terrorist communications (and their Internet message boards) is the need to avoid civilian casualties. The impact of this can be seen in Mali, where Islamic terror groups (including al Qaeda) control most of the sparsely populated (and largely desert) north. Many of the locals want no part of Sharia (Islamic) law and strict lifestyle rules. But instead of killing those who resist (which is still done in places like Somalia and Pakistan) the Islamic radicals fire their guns into the air to break up demonstrations against Islamic rule. If that doesn't work the suspected anti-al Qaeda leaders are rounded up and whipped. But the resistance continues and this worries fans of Islamic conservatism. Even in Saudi Arabia, where strict lifestyle (but not as strict as al Qaeda) rules have been enforced for decades. Popular resistance to this continues and it grows stronger. The message is that what Islamic radicals are selling has a very short shelf life and that most Moslems don't want it after they have sampled it.
Going back to mass murder is not seen as an option. This belief is based on the harsh experience in Iraq. Al Qaeda was enraged when the U.S. and Britain invaded Iraq in 2003. By the end of that year the Sunni Arabs were removed from power and the coalition declared that democracy, and majority rule, would prevail. Democracy was anathema to the Iraqi Sunni Arabs, who, as only 20 percent of the population, feared retribution from the majority (Kurds and Shia Arabs). In addition, there was the money angle. The Sunni Arabs had been keeping a disproportionate share of the oil wealth for themselves and had been doing so for decades. In order to avoid poverty and persecution, the Sunni Arabs began a terror campaign against the coalition (mainly U.S. and British) troops. In early 2004, they allied themselves with al Qaeda and Islamic terrorists in general. Al Qaeda saw the invasion of Iraq as an attack on their heartland and an opportunity to defeat the United States and the West in general.
The war in Iraq did serious damage to al Qaeda. This was because of the many Moslems killed as a side effect of attacks on infidel (non-Moslem) troops, Iraqi security forces, and non-Sunnis. Al Qaeda played down the impact of this, calling the Moslem victims "involuntary martyrs." But that's a minority opinion. Most Moslems, and many other Islamic terrorists, see this as a surefire way to turn the Moslem population against the Islamic radicals. That's what happened earlier in Algeria, Afghanistan, Egypt, and many other places. It really has nothing to do with religion. The phenomenon hits non-Islamic terrorists as well (like the Irish IRA and the Basque ETA).
The senior al Qaeda leadership in Pakistan soon noted the problem in Iraq and tried to convince the "Al Qaeda In Iraq" leadership to cool it. That didn't work. As early as 2004, some Sunni Arabs were turning on al Qaeda because of the "involuntary martyrs" problem. The many dead Shia Arab civilians led to a major terror campaign by the Shia majority. They controlled the government, had the Americans covering their backs, and soon half the Sunni Arab population were refugees.
Meanwhile, the "Al Qaeda In Iraq" leadership was out of control. Most of these guys were really out there, at least in terms of fanaticism and extremism. This led to another fatal error. They declared the establishment of the "Islamic State of Iraq" in late 2006. This was an act of bravado, touted as the first step in the re-establishment of the caliphate (a global Islamic state, ruled over by God's representative on earth, the caliph). The caliphate has been a fiction for over a thousand years. Early on the Islamic world was split by ethnic and national differences, and the first caliphate fell apart after a few centuries. Various rulers have claimed the title over the centuries but since 1924, when the Turks gave it up (after four centuries), no one of any stature has stepped up and assumed the role. So when al Qaeda "elected" a nobody as the emir of the "Islamic State of Iraq", and talked about this being the foundation of the new caliphate, even many pro-al Qaeda Moslems were aghast.
When al Qaeda could not, in 2007, exercise any real control over the parts of Iraq they claimed as part of the new Islamic State, it was the last straw. The key supporters, battered by increasingly effective American and Iraqi attacks, dropped their support for al Qaeda, and the terrorist organization got stomped to bits by the "surge offensive" a year later. The final insult was delivered by the former Iraqi Sunni Arab allies, who quickly switched sides, and sometimes even worked with the Americans (more so than the Shia dominated Iraqi security forces), to hunt down and kill al Qaeda operators.
By 2007, opinion polls in Moslem countries showed approval and support of al Qaeda plunging, in some cases into single digits. After the invasion of Iraq, al Qaeda managed to take itself from hero to zero in less than four years. Al Qaeda is still trying to recover and the kinder and gentler approach does not seem to be working.