Surah 26. Ash-Shuara, Ayah 40

There is no doubt that these "sorcerers" were priests of the official Amon cult, in which magic played an important role. Thus, their victory over Moses would constitute a public vindication of the state religion.

See the last note. The people are to come and witness the triumph of the State religion, so that they may become the more obedient to Pharaoh and more compliant with the demands of the priests. The State religion included magic and the worship of Pharaoh.