The Ghost of Harrenhal - S2-E5
Character mistake: When Renly and Catelyn are negotiating the terms of Renly's alliance with Robb, Renly calls Moat Cailin "Moat Caitlin." As someone who served as Master of Laws on King Robert's Small Council, he should know the correct name of the territory he is referring to.
Answer: This is explained more in the book. Khal Drogo and his bloodriders do intend to help Viserys take the throne, however they do things in their own time. This is what causes Viserys's frustration. In the book, Illyrio Mopatis tells Viserys that he has already waited his entire life to claim The Iron Throne and that waiting a few more years isn't that big of a deal. The Dothraki are a nomadic tribe, which is largely why they have no interest in invading and sacking King's Landing. However, since Khal Drogo eventually grows to love Dany, her assassination attempt by the Westerosi compels him to seek revenge.
Phaneron ★