It might be a coincident that the „Islamic State of Iraq and Syria“ (ISIS) attacked and took over Iraqs second biggest city Mosul – http://www.bbc.com/news/world-middle-east-27778112 – just as the Pakistani Taliban attacked the airport of Karachi, http://www.bbc.com/news/world-asia-27777449

There is more than one parallel between both groups/organizations if one knows the story of the Taliban.

Back in the mid 90s, apart from a very short while when Afghan people thought that the new „students“ movement would bring peace, security and even freedom for their country, disillusion dawned upon the broad majority of Afghans of all ethnicities.
The Talibans adherence to a hitherto unknown extreme understanding of the islamic law, their total lack of familiarity with Afghan history and customs, their unlimited intolerance and hostility towards religious and ethnic minorities alienated and intimidated the population, especially outside of the so called Pushtun belt.
It can be highly recommended to read Ahmed Rashids book about the Taliban movement:
http://www.amazon.com/Taliban-Militant-Fundamentalism-Central-Second/dp/0300163681/ref=sr_1_1?s=books&ie=UTF8&qid=1402425017&sr=1-1&keywords=ahmed+rashid+taliban

The Taliban were not interested in gaining anyone’s sympathy, nor where they seriously interested in coalitions, power sharing or any kind of compromise. While they were clearly sectarian (means anti-Shia/anti-Iran) their biggest enemy was the mainly Sunni „Northern Alliance“, led by Commander Ahmad Shah Massoud. They massacred thousands of Shia civilians but also Sunni Uzbek POWs, just as they poisoned the wells and destroyed the livestock of the mostly Sunni Tajik inhabitants of the Shamali plain.
They simply did  not care about anyone.

ISIS appear to be similar. While the majority of their ruthlessly killed victims are Shias (the majority civilians) they do not hesitate to suicide bomb Sunni clan chiefs, „Sahwa“ militias and civilians.
The Taliban fielded thousands of Pakistanis and hundreds of Arabs, Chechens, Uzbeks, Uighurs and others. ISIS fighters also consist of North African and Gulf Arabs, Pakistanis, Chechens and even European Salafis.
Just as the Taliban shocked the world in the 90s, ISIS does very much the same in recent years. They by far exceed the extremism of other islamist organization, among them even such that themselves are militant Salafis. As a consequence ISIS succesfully and simultaneously fights completely different forces: The predominantly Shia army of Iraq, the mostly Sunni extremist rebels in Syria, the Kurdish militias in North Eastern Syria and at times the Syrian Arab Army.

Both the Taliban and ISIS have their ideological roots and a major portion of their financial backing in Saudi Arabia and to a smaller extent in other Wahhabi dominated Arab countries in the Persian Gulf. The official line of the Saudi government is to declare and regard ISIS an enemy, but the government is at best unable and at worst unwilling to prevent „private donors“ from funding the salaries, the training, the arming and the logistics of ISIS:
https://100wordz.wordpress.com/2013/12/28/al-qaeda-in-syria-and-the-private-donors-from-the-gulf-monarchies/
It was the same with the Taliban. It were the Saudis who bankrolled their offensives by supplying hundreds of gun-mounted Datsun pickup trucks over and over again, while Pakistani Madrassas – often funded by Saudis and preaching Wahhabism – provided the man power.

While the Saudi approach might appear irrational at first sight, it is indeed very rational at least in the short and midterm run:
1. The takfiri Jihadis are identified
2. They are kept away from Saudi Arabia (and the Gulf) by being constantly involved in „Jihad“ from Libya over Syria to Iraq
3. They are inflicting heavy damage and casualties on Shias and their allies

As a side effect but definitely all but incidentally Israel and the US are (at least in secret) very happy that Syria, Hezbollah and also Iran are bleeding and getting damage.

Still, it is puzzling how a seemingly small militia without airpower and heavy weapons has been able to humiliate Iraqs at least 500.000 men strong armed forces.