I the Preacher was king over Israel in Jerusalem.
Resumption of Ecclesiastes 1:1, the intermediate verses being the introductory statement of his thesis. Therefore, the Preacher ( Qohelet (H6953)) is repeated. From this verse to Ecclesiastes 2:26, the Preacher shows the vanity of earthly things from his own experience.
I the Preacher was king - instead of 'am,' because he is about to give the results of his past experience during his long reign.
In Jerusalem - specified as opposed to David, who reigned both in Hebron and Jerusalem; whereas Solomon reigned only in Jerusalem. "King of Israel in Jerusalem" implies that he reigned over Israel and Judah combined, whereas David, at Hebron, reigned only over Judah, and not, until he was settled in Jerusalem, over both Israel and Judah. If ever man had the opportunity of testing whether earthly things can afford solid satisfaction, it was Solomon-a king, and therefore having immense means at his command; and in Jerusalem the center of a then wide and highly favoured kingdom, furnishing a most ample field of philosophical observation, (cf. Ecclesiastes 2:1, etc.) The Preacher begins with human wisdom, for which he was famed even among pagan nations (1 Kings 10:8; Matthew 12:42).