"Maybe it's because I am an outsider - both my parents were refugees," he told the Sunday Times magazine of the series' success.
"If you had told me I would be doing this, I would have told you it was mad, hallucinogenic conjecture. I wouldn't have guessed there would be anything more to say about this countryside woman of limited intelligence who would have much preferred looking after her dogs and breeding horses to being queen.
"But now I'm here. Life is strange."
Saying the monarchy survived the 20th century without "catastrophic errors" from the Queen, he added: "They're survival organisms, like a mutating virus.
"Look at how many prime ministers are wheeled out in coffins, on stretchers, having made fools of themselves: Downing Street is full of sick people. And yet she survives.
"It is clearly a deranged institution and a completely insane system, but perhaps it's the insanity that makes it work.
"Belief in God is so deranged that it makes absolutely no sense, but it holds people together somehow."
The Crown is broadcast in more than 190 countries.
Secured by the streaming service after it outbid the BBC to pay a reported £100m for the first two series, it has become a critical hit.
It won a Golden Globe for best television series with further awards for Foy and John Lithgow as Churchill, along with nominations for Morgan and director Stephen Daldry.
Asked about his version of Royal history, and whether it would go on to become an accepted version of events in the minds of the viewing public, Morgan suggested he approached it differently to a typical biography.
"Authorised royal biographers are so straitjacketed, deferential, fawning and unadventurous that they can only be after a knighthood," he said.
"Or they're completely scurrilous and insolent, like Andrew Morton or Paul Burrell.
"I think there's room to creatively imagine, based on the information we have about her."
He has previously spoken on how he hopes the Royal family do not watch the show, adding he has "no idea and I don't want to know".
The team are not in contact with the Palace over their storylines, which will this series include a fictionalised affair between Prince Philip and a ballet dancer.
After this series, its second, the main cast will be replaced as their characters age, with Olivia Colman reported to be taking over the role of the Queen.
