I think people are being harsh here. Personal judgements should be separate to how much the law and companies should operate.
Even if the flights were booked on July 26th it shouldn’t matter. They were flights operating between countries with no rules attached.
Once the government changed the rules, the airline should have either cancelled the flight or offered a refund. Airlines are equally “taking a risk” by operating flights during the pandemic.
Personally, would I have booked the flights? No. However I can see what’s fair and what’s no fair here and frankly airlines continuing to fly to places the FCO say not to is morally dubious because they know that the customers will then bear the brunt of the costs and not them.
It’s been fairly long standing that once government advises against travel to countries then flights (for the most part) cease. This should be no different.