Did Allah "Start Christianity?"
Christian apologists often argue that if Allah made it appear that Jesus was crucified, then Allah would be responsible for creating Christianity. A basic contemplation over this argument collapses it under its own weight.
The central flaw in the Christian argument is the absurd assumption that merely believing Jesus died on the cross somehow naturally leads to belief in the Trinity, incarnation, atonement theology, and the abolition of the Mosaic Law. That makes no sense whatsoever.
Suppose someone believed Jesus died as a martyr. Why would that logically mean he is God? Why would it mean that God is a Trinity? Why would it mean that his death transfers sins? Why would it mean that the laws practiced by prophets for centuries suddenly became obsolete? None of these doctrines logically follow from the mere belief that Jesus was crucified.
At most, the belief should have led people to think that a prophet of God had been killed unjustly, just as other prophets suffered persecution before him. The later theological inventions were the result of human exaggeration, philosophical speculation, and religious innovation. The blame for that rests on those who invented such doctrines, not on Allah.
Consider an analogy. Imagine someone plays a prank on a man and falsely convinces him that he won the lottery. Instead of simply becoming excited, the man spirals completely out of control. He insults his family, abandons his wife, destroys his car, quits his job, and cuts off all his friends. Later he discovers it was only a prank. Would any rational person say that the prankster is morally responsible for every irrational decision the man chose to make afterward? Obviously not. The prank may have triggered events, but the man himself remains responsible for his destructive behavior. The prank did not force him to abandon morality, reason, and self-control.
Likewise, even if someone wrongly concluded that Jesus died on the cross, that still would not justify inventing doctrines such as the Trinity, incarnation, inherited sin, vicarious atonement, or worshiping Jesus as God. Those were theological choices made by human beings.
Ironically, Christianity faces a far more devastating version of the very argument it tries to use against Islam. Christians believe Jesus was God incarnate, yet nowhere in the New Testament does Jesus plainly and unambiguously say, “I am God, worship me.” As a result, entire groups throughout history rejected his divinity while still accepting him as the Messiah. Even today, Biblical Unitarians continue arguing that Jesus never claimed to be God.
By Christian polemical standards, one could easily turn the accusation around and say: Why did God not make the divinity of Jesus absolutely explicit and impossible to misunderstand? Why leave room for centuries of disagreement? Why enable confusion regarding the Trinity, the incarnation, and salvation itself?
Christians will naturally respond that people are responsible for rejecting the truth even if the evidence is sufficient. Exactly. That same response can be used by Muslims.
The real issue here is not deception. It is human beings taking an event and building massive theological claims upon it without justification. Believing Jesus was crucified does not remotely justify believing he was God, part of a Trinity, or a sacrifice for the sins of humanity.
The attempt to blame Allah for Christianity ultimately exposes a massive double standard. The very principles Christians use against Islam rebound against their own theology with even greater force.
Recommended Reading:

Consider also that it is a stretch to say that when the text says “it was made to appear to them that he was crucified..” to insert “God” for “it”. Meaning, it seems much more likely that Paul’s letters and the gospels written decades later are the tools used which made “it appear to them that he was crucified”.
yes, I see that. I don't understand the trinity and I doubt many do. I haven't read the whole Bible and I doubt many have.
Yet we have all these believers.
I only know I love Jesus and I humble myself before God because I need to, not because anyone told me to.
I had a chat with Muslims who couldn't understand why I worship a man as God. I told them I don't but that I do view him as my teacher.
But I can say his name and I can talk about him as a man.
So, if Muslims don't worship their Prophet, why can't they even say his name? I think that could be called something like worship.