As the article says, it is surprising how easy and cheap it is to shut down a world-class airport and disrupt 100,000's of people. They haven't even caught the last person.
DoS attack doesn't necessarily mean high request volume.
Granted, the chance to get caught is smaller with drones, but it's still fairly risky. I guess the only defense here are publicized arrests to dissuade the "prankster" category of attacker and the fact that statistically only very few people are crazy enough in the first place to try such an attack.
[1] https://www.telegraph.co.uk/news/2018/12/23/gatwick-drone-ar...
What counterpoint are you making here?
Although not before the press had smeared their names and faces across the whole country.