Foreshadowing is not the same as actually developing the character. A show like Breaking Bad spent many seasons turning the character from A to B, despite the hints being there from early on. Disregarding the past 2 episodes, Game of Thrones did it as well with a character like Jaime, changing him through the course of many interactions and events throughout the seasons. There was nothing like that kind of groundwork with Daenarys. The showrunners themselves have also strongly suggested themselves the mass-murder was a spur-of-the-moment thing, not premeditated strategy. Granted though, you can't entirely rely on what they're saying, given how they also said after E03 that the Dothraki were gone.