He's the company president, but his assistant is 'the (real) power behind the throne'.
In Shakespeare's play, Macbeth kills the king and 'ascends to the throne'.
He 'ascended the throne' [=became king] after the death of his father.
(..) It's also the right thing. Do you think I'm the last man she'll execute? Who is more dangerous than the rightful heir to the Iron Throne? That's her decision. She is the queen. I'm sorry it came to this. And your sisters? Do you see them bending the knee? My sisters will be loyal to the throne. Why do you think Sansa told me the truth about you? Because she doesn't want Dany to be queen. - She doesn't get to choose. (..)2019 TvShow: Game of Thrones Title: The Iron Throne Season: 8 Episode 6