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. And exactly this win shows that Afghanistan is still strong team and it sets up exciting match between them in final.
There is nothing surprising in Pakistan's performance. This team's performance is always erratic. Although after Afghanistan gave a target of 170 runs, I thought Pakistan would win. But no batsman could bat responsibly and could not play a big innings. Only because of Haris Rouf's unbeaten innings of 34 runs off 16 balls, Pakistan was able to reduce the margin of defeat a little. If batsmen like Saim Ayub, Hasan Nawaz and Mohammad Nawaz could have played a little better, Pakistan had a chance to win. But the team lost 9 wickets for just 111 runs. If the top order fails to play well on this pitch, it is no longer possible to win.