Why does Allah lead some people astray and guide others, and why did Allah not grant victory to Jesus (peace be upon him) and spread his religion instead of casting doubt upon those who betrayed him?

Allah's guidance - which is the granting of success in faith and righteous deeds - is not attained by everyone. Rather, it is for those who deserve it. Allah Almighty knows best who is fit for guidance, so He guides him, and who is not fit for it, so He leaves him in his error, as He says: "Indeed, you do not guide whom you like, but Allah guides whom He wills. And He is most knowing of the guided." The Holy Qur'an has explicitly stated the characteristics of those who are deprived of guidance, such as "the wrongdoers, the disbelievers, the defiantly disobedient, the liars, the extravagant," and the characteristics of those who deserve it, such as "who follow His pleasure, who turn to Him in repentance, who strive in the way of Allah." This increases certainty in Allah's justice and wisdom. As for the problem related to Allah's wisdom in His divine decree and destiny, it is based on human ignorance, and the overall wisdom of creation is trial, as He says: "He who created death and life to test you, which of you is best in deed." This question is not appropriate for Christians who believe that God allowed His enemies to kill His son by crucifixion as atonement for human sins. The correct belief is that Christ, peace be upon him, was neither killed nor crucified, but it was made to appear so to them.