It's sad news but given the amount of pilots in the air around the globe at any one time, statistically it's going to happen with a certain regularity.
As others have pointed out, some things can be screened for or the risks reduced by a particular lifestyle but some are beyond present predictive science. It's why we have redundancy in the crew over a certain size of aircraft as well as redundancy in the systems.
The 'plane was put safely on the ground, unfortunately one of the pilots didn't make it. From the passengers point-of-view, that worked.
There are many things that can seriously affect your performance to the point that you might as well be dead, like food poisoning, allergic reactions, appendicitis, etc. They can happen to anyone of any age or level of fitness. Changing medical requirements is not going improve anything for this group, which probably accounts for the vast majority of in-flight incapacitations.