Pre- 2011 Pakistan and India were largely in different groups in World Cups (2003 being an exception).
In 2011 Pakistan and India were in different groups and there was no guarantee that they would meet in the knockout stages.
I believe, that the hype and media attention the 2011 World Cup semi final received, made the ICC realise that Pakistan India matches are a money spinner especially given the suspension of bilateral tours between them.
From that point, the ICC ensured that Pakistan and India were placed or seeded in the same group in all ICC tournaments to ensure that a Pakistan India match would always be on the cards. Even the current 10 team round robin format guarantees this match
In 2011 Pakistan and India were in different groups and there was no guarantee that they would meet in the knockout stages.
I believe, that the hype and media attention the 2011 World Cup semi final received, made the ICC realise that Pakistan India matches are a money spinner especially given the suspension of bilateral tours between them.
From that point, the ICC ensured that Pakistan and India were placed or seeded in the same group in all ICC tournaments to ensure that a Pakistan India match would always be on the cards. Even the current 10 team round robin format guarantees this match