As noted previously on this site (quoting Mail-Jewish), there's a general tendency in midrashim to claim two persons in Tanach are the same. This is familiar to anyone who has studied Rashi's commentary on Chumash: for example, Lot is not only Avraham's nephew but also his brother-in-law, and the man who told Avraham of his capture later reigned in Bashan.
While there is doubtless a good reason for this every time it's done, I'm trying to understand the reason for the general tendency. Why do midrashim tend to identify people? What philosophical or religious or textual or rhetorical or other ideal does it further?