When Tutankhamon died, his widow Ankhesenpaaton controlled the country; the man she married would be the new Pharaoh.
The obvious candidate was Horemheb, a powerful and able priest.
But Ankhesenpaaton couldn't stand Horemheb; she refused to marry him and make him Pharaoh, in spite of political pressure.

She tried to find someone else to marry. She is known for having written a letter, which remains, to the neighboring Hittites,
asking the king to send her one of his sons, to whom she would offer herself and the throne of Egypt.

If you could send me one of your sons I would make him my husband.
The king complied, sending her his son Zannanza.
But the young man was intercepted and slaughtered as he entered Egypt, probably by someone loyal to Horemheb.

This behavior on the part of Ankhesenpaaton was totally unheard of. Although Pharaohs had often made diplomatic marriages to foreign princesses, Egyptian princesses were considered too valuable
to be sent abroad; many were married to the only worthy husband, namely their own brother or father. When the King of Babylon,
whose own daughter was married to Amenhotep III, inquired about an Egyptian bride for himself, he was given short shrift:

Since the days of old, no Egyptian king's daughter has been given to anyone.

Then Ankhesenpaaton decided to marry the "Divine Father Ay", an extremely old man who had been Tutankhamon's trusted guide.
She married him and made him Pharaoh, but after just three years he died.
Ankhesenpaaton continued to refuse to marry Horemheb, and departed, leaving him to become the new reigning Pharaoh.