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It was not Selen and her projects.
It was not Rosemi and her mama.
It was not Petra's inability to type due to her flippers.
It was obviously Tazumi Riku's plan to win August Gold Tally. We know he is obsessed with numbers because he debuted a vtuber specifically to celebrate 1 million before their IPO. Nijisanji is desperate for the win so they delayed it to be in the same month as Koushien.
This is the only logical conclusion.