Simply put: They enjoyed doing it. I wouldn't do it. But I would say I definitely see why someone would rather leave this world doing something that brought them joy over something like cancer.
Raw numbers don't mean much unless you normalize to the number of participants in some way and, really, to the level of the activity. Not a lot of people are killed flying in wing suits but that's not because it's such a safe activity.
To be clear, I think mountaineering is a perfectly rational activity for people to pursue so long as they're going into it with their eyes wide open. I've certainly done activities in that vein that some reasonable percentage of people would probably consider excessively dangerous for various reasons.
I wouldn't personally do many of them but I'd hesitate to criticize people in general for pursuing activities that have greater than typical day-to-day danger associated with them.
I clicked through the link and looked at what data was available--looked like a lot of broken links. But, depending on your definition of mountaineering, as someone with a fair bit of experience in the area, I simply don't believe that mountaineering at any significant level is safer than driving whatever sort of normalization you settle on. The latest fatality stats for US roads is something like one per 100 million miles.
However, as both you and the link suggest, it's essentially impossible to normalize. I don't know how I'd even draw a hard line between a "walk in the woods" and "mountaineering." But do whatever works for you.
I think "mountaineering" is probably more dangerous, especially once you get into the alpine.
I do (and love) outdoor climbing and even a bit of mountaineering, but it seems like most accomplished climbers die in the alpine. Some of what people do makes Honnold's famous free solo of El Cap look tame by comparison
There's risk in all manner of things. Some I would personally consider as high risk for relatively low personal reward--or I'm not physically capable of doing them anyway (which alas covers more things than used to be the case).
But people like challenges, experiences, etc. some of which are never going to be wholly risk free. I'm not going to pressure someone to get out of their comfort zone in a way that puts them in potential physical danger but I fully understand people who pressure themselves. I've certainly gotten into some dicey situations now and then. Nothing serious happened--I was generally prepared--but it wouldn't have taken a lot for things to go sideways.
Or maybe you get distracted and forget to look both ways before crossing the street.
Sitting in front of a computer will claim a lot of lives through inactivity but manny people still do it because it brings meaning / relaxation / connection to other people to their lives.
