I came across another interesting article about Iran (you may also like the one about how Iran is the only country in the world where you can legally sell your kidneys). The article argues that even though the state claims to be 99.9% Muslim, only around 40% actually identify as Muslims. The interesting thing about it is that these numbers seem to be actually lower than those before the Islamic Revolution in 1979:
68% agreed that religious prescriptions should be excluded from legislation, even if believers hold a parliamentary majority, and 72% opposed the law mandating all women wear the hijab, the Islamic veil. […]
Over 60% said they did not perform the obligatory Muslim daily prayers, synchronous with a 2020 state-backed poll in which 60% reported not observing the fast during Ramadan (the majority due to being “sick”). In comparison, in a comprehensive survey conducted in 1975 before the Islamic Revolution, over 80% said they always prayed and observed the fast.