Well my mum -- when she started doubting my Muslimness -- went on about how she's never heard of people leaving Islam, only people entering it, in droves, all over the world. She also told me about one of her best friends from school who now lives in Europe and left Islam a long time ago; she told me that she has no community, doesn't belong anywhere, is unmarried/childless and is now sad and lonely. This woman now wants to return to Islam (tbh she doesn't sound like she ever left it through rationalism but rather got lazy and ditched Islam for convenience once she got to Europe) but cannot because the ummah won't have her but she will never be accepted by the kuffar (because she's African? Because she's Muslim-y? I don't know, mum never specified) because she can't *really* become one of them so now she's "lost". She didn't explicitly say it but she was saying this as a sort of cautionary tale for me, warning of the dangers of leaving Islam.
I've learned that my mum sees leaving Islam as betraying your people and trying to be accepted by the kuffar (who have this guttural hatred of anything that is or was ever Muslim); it's a very tribalistic way of seeing things but that's how she sees it. "What's so good about non-Muslims?", "Why would you want to become one of THEM?", "Muslims are good", it's as if it's a family/tribe thing and not a belief thing. I just felt like saying "it's not fucking sports or something, I'm not changing teams; I don't hate or want to be a part of anything, I just don't believe anymore!" but I'm still pretending to be Muslim so
It's a nice system Islam has built; some of the ways it manipulates people, creates intricate self-fulfilling prophecies and rules/structures that work so well at propagating itself plus it's ability to still have followers in the enlightened world despite it's blatant cruelty, misogyny and ludicrousness sometimes made me think "such an excellent memeplex must be divinely inspired!" and Mo may have been quite intelligent.
Islam is shamelessly triumphalist to a disgusting degree; it establishes itself in the minds of it's adherents as the best thing to happen to humanity since...well, humanity, and as being superior to -- and in fact entitled to rule over -- all other systems. Of course it's also taken for granted that Islam is correct. "We hear and we obey" and we don't let the shaitan whisper in our logic into our ears; Islam needs no proof, it is self-evident. This creates arrogance.
Islam commands death for apostasy effectively keeping apostates quiet, whilst celebrating and shouting any conversions to Islam from the rooftops hence allowing Muslims to continue to believe that no one leaves (because Islam is so obviously, undeniably true -- this is why apostates are often accused of being debauched or ignorant of Islam b/c in a Muslims' eyes there's no other reason to leave) and people only join.