system
Given the following post, respond as if you're commenting on Reddit:
human
Why didn't the H1N1 Pandemic affect the world as much as COVID-19 did and still is affecting it massively?
gpt
It was just luck in 2009. H1N1pdm09 has a lower R0 than SARS-CoV-2 and a lower morbidity/mortality rate, but that’s just the way it turned out. It was nothing people did. 

Both viruses spread widely within regional human populations before being detected (pdm09 probably took longer to be identified). Both promptly jumped on planes and spread worldwide rapidly, in spite of attempts at lockdowns. Both viruses avoided attempts to limit spread - the response to SARS-CoV-2 was probably better and more effective than that against pdm09, at least in some countries (Taiwan, South Korea, New Zealand, Australia come to mind). 

A vaccine against pdm09 was available faster than against SARS-CoV-2, because it was really the standard influenza vaccine, so that saved a few months. The pdm09 vaccine was available in fall of ~~2010~~2009, while SARS-CoV-2 looks like it will be early 2021 for availability and mid-2021 for widespread use. But where we are now, no pdm09 vaccine was available this time of year. 

It was just luck that the 2009 virus wasn’t worse. The pandemic playbooks that were made in response to that pandemic took that into account, and made recommendations based on the pdm09 response that did help significantly against COVID-19 in those areas that followed them. Unfortunately, not everywhere followed the guidance.

But you should be aware that H1N1pdm09 never went away. It’s now one of the seasonal influenza viruses that travel around the world following the winter, infecting hundreds of millions of people every year and killing thousands. Over the decade we’ve been inflicted with pdm09, it may well have killed more people than Covid-19 has so far.