You may be right TallPete but I still wonder if it is not MITM.
There a a few reasons for that idea:
There is no evidence yet that the number of people affected is not large. That remains to be seen.
The number of people here with the issue in such a short time is unusually high. That points to a large issue - especially since there is no reason to suppose that the majority of those impacted would come here first.
I would even suspect that there would be a number who would pay... not that they would say so out loud. The amount demanded is relatively small and the method of fixing it relatively arcane to the non-technical user. That makes for payment the easy option.
There is evidence from Apple that until recently iTunes was open to MITM exploit.
Not everybody religiously patched their software and it is reasonable to suppose that there is a significant number of unpatched iTunes out there..
On the other hand - as you say - there could be other explanations.
I think that the significant number of attacks in one night points to a harvesting of Apple IDs and Passwords that has been happening over a number of days followed by a programmed exploit to launch the ransom demand. The quickest way to have achieved that would be to have had a phishing exercise via email or other software infection.
There is also a large number of people whose IT security practices make phishing easier.
The fact that the issue seems local to this region could be related to the vector of deception.
The weak point in the attack is that the actions taken did not prevent a fairly simple restoration. It might be that the hijacking of the whole account either was not possible in the time frame allowed for the attack - or that the attacker was only 'almost clever'.
It will be interesting to see what the story is when it comes out in the fullness of time.