I predicted it a day before and afghanistan did win against Pakistan. Sediqullah Atal and Ibrahim Zadran's coincidental aggressive scoring with almost same runs in same balls, 64 of 45 and 65 of 45 respectively propelled Afghanistan's score to a defendable one.
Pakistan got a target of 170 which is not a huge for T20 but their batsmen failed to deliver, they were trying to score but occasional wickets made them always lower than the required run rate. Saim Ayub was a golden duck. The result shows Afghanistan is still capable but its still depended on the older generation. But the result of this T20 is not as significant as Pakistan and Afghanistan would eventually meet at the finals later.
You made correct prediction and your analysis of match is good. Afghanistan win against Pakistan was largely due to great batting of Sediqullah Atal and Ibrahim Zadran their partnership set strong target of 170 runs. And from Pakistani batsmen including Saim Ayub got golden duck struggled to score runs because of losing wickets quickly.
ThisAnd exactly this win shows that Afghanistan is still strong team and it sets up exciting match between them in final.