Because that Tyrus, etc. As the nearest great commercial city, the Venice of the ancient world, Tyre, from the days of David (2 Samuel 5:11) and Solomon (1 Kings 5:1) onward, had been prominent in the eyes of the statesmen and prophets of Judah; and Ezekiel follows in the footsteps of Joel 3:4; Amos 1:9, Amos 1:10; Isaiah 23:1-18; in dealing with it.
The description in Isaiah 23:5 and Isaiah 23:14 points, not to the city on the mainland, the old Tyre of Joshua 19:29, which had been taken by Shalmaneser and was afterwards destroyed by Alexander the Great, but to the island-city, the new Tyre, which was, at this time, the emporium of the ancient world.
The extent of her commerce will meet us in Ezekiel 27:1-36. Here, too, as in the case of the nations in Ezekiel 25:1-17; Ezekiel's indignation is roused by the exulting selfishness with which Tyre had looked on the downfall (actual or imminent, as before) of Jerusalem.
"Now," her rulers seem to have said, "we shall be the only power in the land of Canaan." Jerusalem, that had been the gate of the peoples, was now broken.