If Islam is the "Most Accurate" Then Why Are There More Christians in the World?

In the Name of Allah, Most Merciful and Compassionate

I'm going to restate the question.

"If Islam is true then why are there so many people who are not Muslim?"

This question is assuming a necessary (or probable) relation between the truth of Islam and the number of people who are not Muslim. 

In other words, it is assuming the truth of the following if-then statement:

If Islam is true 

then most (or all) people in the world will be Muslim.

This statement is equivalent to the following statement:

If most people in the world are not Muslim

then Islam is not true.

In other words, we should judge the truth of a belief based on the number of people who hold it. 

That means that if many people hold it, it must be true. 

And it also means that if few people hold it, then it must not be true.

This is an incorrect way to analyze truth. 

The way to analyze the truth of a belief is not to count the number of people who hold that belief, but to examine the evidence for that belief. 

If the evidence proves that the belief is true, then the belief is true even if few people hold that belief. 

And if the evidence proves that the belief is false, then the belief is false even if many people hold that belief.

That is why, in the beginning, when the Prophet (Allah bless him and give him peace) called people to Islam in Mecca, the Muslims were few in number. The majority of the people in Mecca didn't believe because they refused to use their minds and insisted on clinging to the ways of their ancestors. They were committing the same fallacy that this question is committing. They were measuring the truth of a belief by the number of people who believed it was true rather than by examining the evidence.

And Allah Most High censured them in many verses for doing that. He said, for example:

“When it is said to them, ‘Come to what Allah has revealed and to the Messenger,’ they say, ‘What we found our ancestors upon is enough for us.’ Do (they cling to the beliefs of their ancestors) even though their ancestors did not know anything, nor were they guided?” (Quran, 5:104)

The point of the rhetorical question at the end of this verse (and many others like it) is to censure them for not using their minds and instead blindly following what everyone else is doing just because they are in the majority.

An important takeaway from this answer is that people don't merely hold beliefs because they are true. They also hold beliefs because of social pressures, personal interests, the difficulty of going against the grain, or the lack of knowledge. Allah Most High has made us responsible to use our mind and hold the correct belief even if most people are believing something else. 

What that means is that the first obligation of every human being is to examine the evidence for Islam to evaluate whether or not it is true, and to accept it as true after they see the evidence for its truth. That what the Prophet Muhammad (Allah bless him and give him peace) called the people of Mecca to do. Those of them who responded to his call became his Companions (may Allah Most High be pleased with them).

Unfortunately, this basic and most essential part of the message of the Prophet Muhammad (Allah bless him and give him peace) is not well-known. 

I teach it in the most important course at Basira: Why Islam is True. I also train teachers to teach the course to students of their own.