Indeed, we have believed in our Lord that He may forgive us our sins and what you compelled us [to do] of magic. And Allāh is better and more enduring."
Fir`awn's turning against the Magicians, His threatening Them and Their Reply
Allah, the Exalted, informs of Fir`awn's disbelief, obstinance, transgression and haughtiness against the truth in favor of falsehood. When he saw what he saw of the magnificent miracle and the great sign, and he saw those whose help he sought accept faith in the presence of all of the people, and he was absolutely defeated, he began to behave arrogantly and cast accusations. He resorted to using his esteemed honor and might against the magicians. He warned them and threatened them saying,
ءَامَنتُمْ لَهُ
(Believe you in him (Musa)) This means, "Do you have faith in him"
وَمَا أَكْرَهْتَنَا عَلَيْهِ مِنَ السِّحْرِ (And the magic you had compelled us on - 20:73). The magicians now accused the Pharaoh of having forced them to practice magic else they would not have taken it up. Here a question may arise that the magicians came to the contest of their own free choice and had even negotiated beforehand their reward if they were victorious. How, then, could they justify their accusation that the Pharaoh had forced them to practice magic? A possible answer can be that whereas the magicians, to begin with, were tempted by promises of generous rewards for taking part in the contest they soon realized that they stood no chance against miracles and wanted to withdraw from the contest. It was then that the Pharaoh forced them to take up the challenge of Musa (علیہ السلام) . Another explanation is that under a law passed by the Pharaoh everybody was compelled to learn magic.
The propitious end of 'Asiyah ؓ ، the Pharaoh's wife
Qurtubi has mentioned in his commentary that while the contest between vice and virtue was in progress, the Pharaoh's wife kept herself informed of the minute to minute developments and when she learned that Sayyidna Musa (علیہ السلام) had emerged victorious, she at once declared her adherence to the True Faith. When the Pharaoh was informed of his wife's defection, he ordered that a huge rock be thrown upon her. When 'Asiyah saw the rock coming, she raised her eyes in supplication to Allah who took away her soul so that the rock fell on her lifeless body.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 73–75
The magicians, on the one hand, were confronted by the cogent reasoning of Moses, and on the other, the towering personality of Pharaoh. The magicians preferred convincing arguments to authoritarianism, although they knew very well how dearly they would pay for their choice. The magicians’ faith was not of the hereditary or formal, ritual kind: it amounted to a ‘discovery’ for them. And faith received as a discovery is so powerful that under its influence everything else appears worthless—be it a great personality or some other worldly consideration.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.