ٱذْهَبْ إِلَىٰ فِرْعَوْنَ إِنَّهُۥ طَغَىٰ ۝١٧ Why does فِرْعَوْنَ show fatḥah after the preposition إِلَىٰ?

Surah An-Nazi'at — Part 2

• It is an object in the accusative
• It is an imperative
• It is diptote, so fatḥah marks its genitive case
• The preposition has no effect