I'd love to know why.
As much as Cilic's shortcomings and mental meltdowns against the top guys are highlighted, he has mostly only been losing to them in the biggest events this year. In almost every Slam and M1000 it has taken one of the current top 3 or Del Potro to take him out (in Slams, Delpo in FO, Murray in W and USO, didn't play AO, most recent Masters Nole in Cincy, Fed in Shanghai). In a tournament where the guys qualified for the WTF are bound to skip or tank, you have to fancy his chances.
Cilic is no match for top players. Raonic is serve-only and Isner too. If a guys returns half of the first serve, the match is over. And Djokovic, Federer and Murray can do that with ease.
plus, to win it, Cilic being a top 16, must beat a top 4 then a top 4 then a top 4. so in the better case: Ferrer, then Federer then Djokovic.
He will lose in QF to a top 8, like Raonic, like Isner.