I'm assuming by 'Dark Mirror' you mean 'Black Mirror', and not 'Dark'? Well, Black Mirror was actually created by Charlie Brooker and his production company Endemol for Channel 4 in the UK and simply bought by Netflix once it was already a hit.

Part of the issue is that many of what Netflix calls "Originals" are the opposite of that and I think it can be confusing for viewers when you throw them into the same bucket as the actual Netflix productions such as The Crown, Stranger Things, Ozark, etc. These are the risky shows, because they had to go out on a limb to green-light them, whereas many of their other "Originals" are actually just acquired and existing successful franchises.