I know this is an unpopular opinion, so please hear me out. There are multiple reasons why Alia won the award for RRKPK:
According to the Filmfare awards website, the nominations for the popular category are chosen by the public. After the nominations are announced, there is a "popular" jury which comprises of filmmakers and actors from the industry who give their votes for the popular awards. It is a well known fact that the industry (From Kapoors to Akhtars to SRK/Kjo camp) loves Alia Bhatt and they would always vote for her if given a choice between her, Kiara Advani and Taapsee Pannu.
Rani Mukerji was a solid contender for the "popular" award, however, her film was a "below average" film at the box office. The "popular" category rarely gives an award to some one who starred in a flop/below average film.
Popularity of Alia's character in RRKPK: Her intro theme, her sarees collection, acting everything was on point and became really popular with the audience.
It's not Alia's fault that no other actress at the moment has been able to create such kind of an impact. She literally has no competition in the industry right now. I won't be surprised if Alia breaks Dilip Kumar's record of 8 filmfares by the age of 36. That would be unfortunate but it would also consolidate her position as the biggest female star of hindi cinema.
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