The increase in Taliban violence in Afghanistan over the last year has been caused mainly by money. Terrorism supporters in the Middle East (mainly Saudi Arabia) moved 5-10 million dollars to Pakistan to fund the current fighting. This is known from interrogations of captured Taliban fighters, and months of Afghan and American troops wandering around the back country of southern Afghanistan and just talking to people. The U.S. Army Special Forces are particularly good at this, since many of them speak the local languages, and have developed many contacts in the rural areas.
It goes like this. Taliban leaders, many of them returning from exile across the border in Pakistan, showed up in Afghanistan last year with lots of cash. That, plus their tribal and family contacts, enabled them to hire hundreds of fighters. For unemployed, or under- employed, Afghan young men, this was an attractive offer. The recruiting was going on among pro-Taliban tribes. If you signed on, you got $300 cash up front, plus $150 a month for 6-10 days of work a month. That compares to $50-100 a month for a full time job, if you could find it. Many of these guys keep their Taliban activities quiet, for there are a lot of people who support the new national government, or simply were mistreated by the Taliban in the past and haven't forgotten. The government also pays for information.
The Taliban also pays for results. You can earn up to $5,000 for killing a government official, or a few hundred bucks if you kill a cop or soldier. Blood money is an old custom in this part of the world, and this encourages the newly enlisted Taliban troopers to hustle when they are on a mission. But these tribal warriors are not suicidal. Their "combat operations" usually consist of going to villages and making threats. Mainly they are terrorists. If they come across an opportunity to destroy a government building (district headquarters, police station, or school) without too much risk, they will do it. Same with ambushing troops or police, or other government employees. These hired guns know how quickly the Americans can have an A-10, an Apache helicopter, or AC-130 gunship, on the scene. So they avoid situations involving people who might call the Americans. If American airpower catches up with you, it's early retirement time. The Afghan army and police have also been improving their rapid reaction forces, and often send people in pursuit who also know the neighborhood.
But in a country where the average life-expectancy is under fifty years, and a man who makes money through violence is respected, and hiring oneself out to the Taliban is a reasonable career choice. It appears that no more than ten percent of the Taliban gunmen really believe in the Taliban cause. It's all about "show me the money" for most of them. Moreover, working for the Taliban is actually safer than hiring on with one of the many drug gangs. These guys move serious amounts of valuable drugs and other goods, and there are many freelancers (bandits) out there who would kill you for it.
The U.S. government is trying to cut off the Taliban money at its source, and has been more successful at that than is generally known. This is because tracking down money transfers is not sexy work. It's not really newsworthy. A lot of the work is done on computers. People pounding keyboards does not make for riveting visuals. Equally important has been the efforts of Middle Eastern governments to crack down on fund raising for terrorists. A lot of money has been stopped, but it doesn't take much to get a few thousand gunmen on the payroll. The Taliban activity rises and falls depending on the amount of cash is available each month. It takes less than a million dollars a month to keep the current "war" going. The Taliban aren't making much real progress. They are trying to terrorize people into either supporting them, or not turning them in. Burning down schools and attacking road building projects just antagonizes the locals who benefit from those things.