Final answer:
The suspicion between Alfonso VI and El Cid likely originated from the intricate web of political and social tensions in the Iberian Peninsula during the time of their conflict, marked by struggles amongst Christian and Muslim rulers and between the monarchy and nobles.
Step-by-step explanation:
The suspicion between Alfonso VI, the king of León and Castile, and Rodrigo Díaz de Vivar, known as El Cid, is believed to have originated from political and social tensions of the time. Conflicts among Christian kingdoms, as well as between Christian and Muslim rulers in the Iberian Peninsula, created an environment of distrust and power struggles within the region. Alfonso's suspicions may have been amplified by the complex web of allegiances and the ongoing power dynamics between nobles and the monarchy. The exact reasons for El Cid's exile are not clearly documented in The Song of the Cid, but it is likely that political machinations and possibly El Cid's own actions, perceived or real, contributed to Alfonso's decision to exile him.