I think you had the ‘perfect storm’. You had various guys walking around with significant pains from high school and college sport injuries. You had people already in their 30’s who had work-place injuries or accident-situations. Their only real relief before....was alcohol, lots of it.
Opioids arrived and deadened the pain. Sadly, if you had any kind of liver issue prior to opioids...well, it just doubled up problems. I think the alcohol consumption crowd had already screwed around with their liver a bit, so opioids just took it to the final level.
Once they dumped the pain clinics....these folks just went to the local dealer and asked what came close enough, and got their dose from that guy. The rest is history.
They are going to heroin because of the pain. They are going because of the addiction.