The proconsul most likely found out about Barnabas and Saul from Bar-Jesus. Since the court astrologer would be responsible for bringing news about new powers and claims to power, it makes sense that he was the source. If this is the case, Elymas probably did not expect the message of Saul and Barnabas to be particularly persuasive (see 1 Corinthians 1:21–25). As for the proconsul, since he is eager to promote peace and prosperity, he wants to learn as much as he can about foreigners and any messages which they may be proclaiming in his capital.
7 He was with the proconsul, Sergius Paulus, a man of intelligence, who summoned Barnabas and Saul and sought to hear the word of God.