In this article, Theo does a good job of breaking everything down. Essentially from what I can gather, Dempster fucked himself over with going to the Dodgers because he wouldn't let it go that they weren't going to increase their offer to the Cubs.
Epstein gave a detailed explanation of the Dempster trade saga, confirming that Dempster was informed of the possibility of being traded to Atlanta 2-3 days before the deal was leaked to the media.
So, Dempster knew about the possibility of a trade before hand, but the talks were obviously premature.
Epstein said Dempster shouldn't be criticized for using his 10-and-5 rights to veto the trade, but conceded it hurt the team's leverage in talks with the Dodgers, who weren't budging. The Cubs wound up getting a lesser deal from Texas, acquiring two Class-A prospects.
"It created a market of one up until about 15 minutes to go (before Tuesday's trade deadline)," Epstein said. "That's just the nature of 10-5 rights. It allows a player to say 'I won't be traded, period.' And Ryan didn't do that.
The Dodgers were smart, knowing that Dempster wanted to go there and after the deal to Atlanta was leaked, they stood on their initial offer and didn't budge. It made total sense on their part. Why give up more if you don't have to?
So Dempster stuck with the longshot of going to L.A., and the Cubs paid the price. Dempster said he never said "no" to the Atlanta deal because he didn't get a chance before the trade was all over the Internet. Epstein said that was not totally correct.
"He didn't technically say 'no,' " Epstein said. "He said 'No, not now. I'm not going to go to Atlanta before I see about L.A.' And Atlanta, very reasonably, didn't want to wait around and risk not getting a pitcher."
And at the end of the day, why should Atlanta wait around for Dempster to make up his mind if he wanted to go there in the first place, when they wanted to start contract negotiations with him? It just ended up not making sense for either the Dodgers or Braves, and the Cubs ended up paying the ultimate price because of Dempster's stead-fast desire to go to the Dodgers.
http://articles.chicagotribune.com/...1_1_theo-epstein-ryan-dempster-trade-deadline