flu deaths are almost all in multiple morbidity patients, usually elderly nursing home residents with less than one year life expectancy (85%), cancer or immunocompromised are next, with little kids with immunity issues completing profile.
I had a flu death in my family that was a teenager. I am not convinced it was really the flu but that was the diagnosis. Death happened with a few days from pneumonia and sepsis. No known immune issues. Coma happened 4 days after first flu symptom. Death later that night.
Just like covid. A few young, apparently healthy people succumb from both diseases as well. When people say “just like the flu” it is only because it...is.
Stuff happens.