Why are some Muslims apostasising from Islam?

In A Nutshell: All aspects of Islam are not 'rational', meaning you cannot logically explain every ruling. There are aspects of Islam that are supra-rational, beyond the realm of rationality. Islam also requires contextualising as a civilisation - each rule fits dovetails with other rules, structures and institutions to achieve this. To reject Islam because you cannot comprehend the supra-rational is irrational; because you cannot understand the civilisation is ignorant. Yet, murtads routinely do this.  Clarifying Important Assumptions Islam was revealed as a way of life, a deen, or as the British-Pakistani Anthropologist Talal Asad terms it, "a discursive tradition". What does this mean? It means it was intended to guide humanity as to how to live - how to organise their societies, how to structure them, how to govern them, how to dispense justice, how to allocate resources, how to achieve prosperity and importantly, how to treat each other all to please God. Following the colonisation of the Muslim world by European powers, this way of life, its institutions, laws and structures were demolished and secular nation states were created. The effect was immediate and dramatic - the Muslim world fell from the proverbial cliff. The Muslim world remains wallowing in decadence, impoverishment, ignorance, insecurity and ignomany. Islam has been reengineered into a religion, a secular, hollowed-out, personal faith - akin to Judaism and Christianity in the West. Many Muslims assume this new religion is the same as that revealed by God. It is not. The Apostasy Project The first issue that causes doubt and confusion for Muslims is trying to make sense of Islamic rules. Most cannot. They make little sense in a secular world. They weren't meant to. They were revealed to construct a civilisation. They weren't meant to be followed selectively under a secular state. It is why most were never revealed in Mecca during the prophet's era - but in Medina. Most Muslims then follow them the rules blindly, not bothering to make sense of them, stating God ordained them when uncomfortable questions arise, giving them little further thought. For others however the seeds of doubt and suspicion grow... and rightly so.  How can one be persuaded of divinely inspired laws that make little sense? or self-contradict? or create more problems than they solve? or seem out of touch with the contemporary age? This ultimately leads to doubt in their divine provience, or even in the divine itself, when they notice society nor its leadership is really committed to these ideas. By rejecting Islam and God, they become neo-murtads rather than murtads. Murtads are apostates who abandon Islam the deen whilst living in an Islamic polity. Neo-murtads are those who abandon Islam the "religion" whilst living in secular nation states. This would not be a problem if they continued reflecting on the world around them and figured out the truth. Most however do not do this - emotions get in the way that clouds their judgement and thinking and a knee jerk reaction leads them to adopting secular ideologies and beliefs of various kinds. This then creates a myriad of problems for which they have no answer.  They then struggle for meaning in empty, vacuous and inconsequential lives - life without God is a depressing reality. A Neo-Apostate's Life Neo-apostates tend to overcompensate by aggrandizing their own pseudo-intelligence, always trumpeting the imagined victory of their 'rationality' over what they themselves have deemed irrational beliefs. In reality, all they have done is to replace their previous supra-rational beliefs they held as Muslims with an even longer list of irrational assumptions they must now blindly believe as murtads.  They convince themselves of finding meaning and beauty in otherwise transient and semi-futile aspects and endeavors, not realizing proof for God is screaming at them throughout the universe. Why even desire meaning and appreciate joys if we are only sub-atomic particles randomly combined to live and breathe? Deaf, dumb and blind, they will not return, unless Allah wills.  Their apostasy is both a rational problem and a spiritual one. To 'submit' to Allah (the linguistic meaning of Islam) requires a level of humility and recognition of the limits of the mind, something murtads do not have. It is why the arrogance that exudes from them is palpable.   But not all hope is lost. Recently, an acquaintance who had converted and then left Islam, re-accepted it. When asked why, he said a parent had passed away in front of his eyes. The reality of life and death, the truth of Islam, all came back to him in an instance. He knew there was no alternative but to submit to Allah.  Conclusion If someone you know has left the faith, if there is any sincerity in them, if they continue reflecting, they will return.  If there is no sincerity, their departure has not harmed Islam but they have only harmed themselves, for their worldly existence has become bereft of all meaning and purpose.