Airspace Closure Insurance Cover Exists
The reality is that even during the events of the ash clouds, there have been insurers that did not recognise (or have been forced not to, whatever you like most) this even as an act of God and provided coverage.
HSBC was among these.
MOL and his lawyers knew this.
For a big airline it should not be an issue to negotiate a good deal for a "tailored" travel insurance to charge back to the passenger.
I see the points that EU is full of bureaucrats, but it is also true that most people are far from being able to self covering themselves (for many reasons, including those who are generally unaware). Therefore minimum compulsory protections should apply.
Like the car insurance, if you wish.
Ulxima