—。
Aegis Collision — Why Couldn't It Be Avoided?
Literal
Aegis collision — why could-not-be-avoided [question-か].
News-headline register. 避けられなかった is the negative past potential form of 避ける 'avoid': 'could not be avoided.' The em-dash separates a noun-fragment topic from a reflective question, a characteristic headline convention. Likely refers to the 2008 collision between the JMSDF Aegis destroyer Atago and a fishing boat, a major news event at the time. The trailing か with no explicit verb before it gives the rhetorical-question feel typical of editorial headlines.