"Silent" here means in part "a lack of public awareness, a paucity of explanatory research, and the reluctance of men to seek help for suicide-related concerns"

"Silent" here means in part "a lack of public awareness, a paucity of explanatory research, and the reluctance of men to seek help for suicide-related concerns". The assertion is that the low ranking you mention is made through general societal ignorance. Compare, for example, to the high number of deaths caused by driving. Those risks are well known, taught in schools, and discussed often. This is a much more informed ranking.