Most of these terrorism deaths were about politics, even if Islamic terrorists were often the killers. A major source of terrorism in the world is the widespread custom of political parties maintaining armed auxiliaries to intimidate their opponents and anyone who might vote for their foes. Often these armed supporters are a local criminal gang, which is more interested in cash than politics. Governments sometimes come to their senses and try to shut down some of these gangs. This is difficult to do. It’s especially difficult in Karachi.
Karachi is Pakistan's largest city, with 14 million people (eight percent of the nation's population) and producer of a quarter of the GDP. Since Pakistan was founded in 1947, there has been violence between the natives (Sindis, from the surrounding Sind province) and new groups from India (Mohajirs, Indian Moslems forced to flee the religious violence that accompanied the division of British India into Pakistan and India in 1947) and Pushtuns, Baluchis, and other minorities from the Pakistani tribal territories.
Politics is often a contact sport in Pakistan and it's become common for political parties to ally themselves with criminal gangs to win elections. The gangster chiefs sometimes seek to enter politics themselves or demand more favors from their patrons than the parties can justify. The gangsters are also, well, gangsters and have unsavory reputations, despite the occasional Robin Hood type gesture. Political parties and their gang associates often part company for political, financial, or personal reasons. Most of this mayhem is concentrated in Karachi and increasingly the actual killers are Pushtun tribesmen hired for that purpose.
The Pushtuns are the most numerous tribal minority in Karachi but are divided by religious and tribal differences. There had long been small numbers of Pushtuns in Karachi but in 1947, hundreds of thousands of Mohajirs showed up. That led to a sharp growth in the economy and that led to more Pushtuns. Enterprising young Pushtuns fled the poor, and violent, tribal lands for a better life in Sind, and often it was these enterprising Mohajir refugees from India that provided jobs and other opportunities. The Pushtuns also found themselves shunned and feared in Karachi because of their alien tribal ways. Meanwhile the wealthier and better educated Mohajirs were soon competing with the Sindis for control of the great city. The Pushtuns and other tribesmen produced a lot of criminal gangs and a poor underclass. On top of this there was also religious violence between various Moslem groups (especially Sunni and Shia) as well as between Moslems and non-Moslems (usually Christians and Hindus).
What makes this such an incomprehensible mess is that each group has a different idea of what winning is. Most of these groups see political power as useful and attach themselves to one political party or another. But political power is a means to an end. The old Sind clans in Karachi want to maintain the power they have held for centuries and have nowhere to go but down. The Mohajirs have hurt the Sind clans economically and politically. But for sheer body count the Pushtun groups (both political, criminal, and religious) have been the most dangerous. The Pushtuns are pushing for respect and more economic and political power. The Sindis and Mohajirs are reluctant to give it up to the Pushtuns. The religious radical groups (including the Taliban and al Qaeda) want a regional religious dictatorship. This puts them at odds with the Sindi and Mohajirs political parties.
In the last three years the violence has gotten much worse. Massive police efforts reduced the violence for a while but the political and terrorist gangs kept at it. Police were ordered to "shoot on sight" any of the armed men responsible for turning many Karachi neighborhoods into combat zones.
While the violence is mainly driven by political parties seeking to establish control over parts of the city, Islamic radicals are heavily involved. The Taliban has established a presence among the two million Pushtuns in the city. Many of those killed have been Pushtuns, partly because the locals are hostile to Pushtun groups gaining more power and partly because many Pushtun groups are fighting each other and most of the best hired guns are Pushtuns. But a lot of the violence is the result of the Taliban trying to prevent the police from stopping the Pushtun radicals establishing safe havens in Karachi. The wealthier Sindis and Mohajirs just want law and order so that commerce can continue uninterrupted. Some of that commerce is illegal, like gun running and drug smuggling. The Pushtun gangs control a lot of this but getting stuff in and out of the country often requires cooperation from Sindi and Mohajirs officials and gangsters.
Karachi is one the wealthiest parts of Pakistan, but the city itself is an explosive mélange of hostile groups. Add to that party politics and a disdain for rules and laws and you get a very ugly situation. It’s not just the deaths, but the kidnappings, robbery, and extortion that gangs carry out when they are not killing for their cause. The chaos seems endless and unstoppable.