Congrats, Cersei. You played yourself. Or so goes a Game of Thrones fan theory currently making the rounds. Over on the Game of Thrones subreddit, user... y'know, I don't think I can publish that username, so let's just say 'a fan' has made an interesting point about Queen Lannister's dealing with the Iron Bank of Braavos.
The fan notes that Tycho Nestoris, who represents the bank and its interests, straight-up told Cersei that it does not bet on who will win and who will lose, but instead invests only in current victors. Nestoris also goes out of his way to flatter Cersei and make mention of her paying off the Lannisters' debt.
"This is her big mistake," the fan writes. "Tywin was no fool and he knew that while the Lannisters were in debt to the Bank the Bank had a vested interest in their success. By paying the debt in full Cersei has allowed Tycho to wash his hands of the Lannisters altogether. After what we saw on the battlefield we have a good idea whose position is strongest and who the Bank would like to back. ... The irony of this theory is in this case the Lannisters are undone by paying their debt."
It's an intriguing thought to ponder, for sure. Cersei has certainly proven herself to be short-sighted before, but she's also quite ruthless in going after what she wants. The actor who plays Nestoris, Mark Gatiss, said that showrunners Daniel Weiss and David Benioff have already "plotted [his] doom," so it'll be interesting to see how this all goes down.