Why would people go after such a hard target when there are so many easier systems that could be hacked, such as land based military installations, nuclear powe

Why would people go after such a hard target when there are so many easier systems that could be hacked, such as land based military installations, nuclear power stations, airports (especially air traffic control), world finance etc? It's probably not totally crazy that one day almost the entire UK NHS or even the US election could be susceptible to a cyber attack, then we'd be really screwed.