Primarily death was due to bacterial pneumonia, the cytokine storm likely accelerating the deterioration of the lungs. That particularly viral strain may have been more dangerous, but overall the current pandemic is comparable in death rates.

It would seem during the Spanish flu your best chance of survival was being in a location where strict quarantine and travel restrictions were imposed so the health system was able to cope with those who did contract the virus.

The places with the highest fatality rates were those with poor or non-existent health services or where people didn't seek medical assistance.

The mortality rate in the US was around 0.5%, <1% in East Asia, but 5% in India and as high as 20% in some Pacific nations. Iran's current Covid-19 mortality rate is quite comparable to the Spanish Flu around 14%.