Maybe he knew if he took 7 sick days his €200 bonus would be slashed?
So three people is the answer? What happens when two of them conspire to do something when the third isn't watching? Do we get four?
This tragic soul is an outlier amongst human beings, not just amongst pilots. Yes, our industry will need to be seen to respond with some procedural change that typically won't cost the airlines anything, but will probably significantly inconvenience the tens of thousands of pilots who turn up to work and get the job done every day. The fleet office will whack a zero tolerance policy on omission of the new procedure on the next line check, and so it goes on.