It's likely a combination of things, but two of the biggest are:

1. Men on average isolate more, keep smaller (sometimes non-existent) social circles, and are less likely to reach out to others for support when they do have friends/family. Isolation is highly correlated with substance abuse of all kinds.

2. Men are on average the higher risk takers. Be it nature or nurture, men disproportionately push safety boundaries for just about anything humans do, which results in high usage of drugs, higher overdose deaths, higher rates of severe accidents, etc.

I feel like older men haven't internalized positive masculinity as much as younger men, so i wouldn't be suprised if men of a certain generation are driving down life expectancy because they self medicate at an even higher rate than women of that age group.

Clarification: Reason I say its older men is cause I'm picturing it being life expectancy, so older men doing worse things to their body kills them earlier. Also, we still have a long way to go with men and not saying younger women and younger men will not still have a disparity on unhealthy/destructive behaviors