Sadly, it's a combination of faulty equipment and poorly trained personnel. As an example, when the Fitzgerald got hit by another ship, reports indicate the radar wasn't working properly and those in charge knew it. It was hard to evade the other ship when the radar didn't show it. Also, I haven't read anything about having actual lookouts on duty.
In 2011, while troops were still being deployed to Afghanistan, the Pentagon reported 395 combat deaths and only two training deaths. But by 2014, as troops were pulled out of Afghanistan and Iraq, combat deaths fell to 38 and training deaths were at 15. In 2015, the numbers reversed with 15 combat deaths and 24 training deaths. In 2016, there were 16 combat deaths and 20 training fatalities. By 2017, using the congressional statistics, training deaths were at 80 and combat deaths at 21.
So far, the training death rate in 2018 seems to be on pace with 2016, a year in which 35 pilots and crew members died, according to the Military Times analysis. Since October, when the fiscal year began, there have been 15 fatal accidents. There was at least one ground incident at Camp Pendleton, in February, when a flight surgeon was struck by a helicopter's tail rotor.
More @ ANALYSIS | More military dying in training than in war; here's what's being done about that