In Game of Thrones' season 7 finale,
Sansa Stark charges Lord Baelish with murder and treason, including the murder of Lysa Arryn, conspiracy to kill Jon Arryn and conspiracy with Cersei Lannister and Joffrey Baratheon to betray Eddard Stark, thus starting the War of the Five Kings.
What events led the Stark children to deduce Littlefinger's plans? — obviously at least some degree of Greensight is to thank, as implied by Bran saying
However, there is at least some suggestion that Arya knows more than what she says even before that moment, given that
Was there any hint at all about how the Stark children connected the dots, or is this all thanks to an act of deus ex machina by Bran?