What Does Yosef Think?
At first glance, the interpretation of Rashbam and Chizkuni seems to explain the psukim much better than that of Rashi. Why then does Rashi explain in a different manner?
Most likely, Rashi and Radak base their "shita" on a key pasuk in Parshat Va'yigash. There, when Yosef reveals himself to his brothers, he states:
"I am Yosef your brother, whom you sold to Egypt." (45:4)Yosef states explicitly that his brothers sold him! Given this 'fact,' it is difficult to explain the psukim in Va'yeshev in any other manner, despite the various difficulties which Rashi's interpretation present.
The Rashbam, bothered by this pasuk, explains that Yosef means to say, "who caused me to be sold to Egypt." However, that explanation is clearly 'reading between the lines,' and does not appear to be "pshat."
Based on the above shiur, one could suggest that Yosef truly did think that his brothers had sold him, even though they themselves never knew what really had happened.
Let's consider these events from Yosef's perspective.
Yosef was not aware of the conversations between his brothers or of their three plans. All that he knew was that as soon as he arrived, his brothers took off his coat and threw him in the pit. A short time later some Midyanim passed by, took him out of the pit and sold him to the Yishmaelim, who later sold him to the Egyptians. Yosef, trying to piece together what happened, may have assumed that his brothers had this all planned out with the Midyanim. Since his brothers did not have the 'guts' to watch him scream, they preferred not to be present when the Midyanim took him away.
According to this "shita" Yosef was totally unaware that it was only 'by chance' that the Midyanim were passing by. In fact, he had no idea that his brothers originally planned to kill him. [In next week's shiur, we will see how this understanding helps explain Yosef's behavior during his many years in Egypt.]