When why not just make a copycat brand. I thing the success of this brand is just survivorship bias. There is nothing special about it but the branding.
Here's the reason: people who drink have weird feelings about being around non-drinkers.
I've been on both sides of this: I have a straightedge tattoo. I didn't start drinking till my late 20s, post college. I now drink... probably a bit too much at times, if I'm honest.
Back when I didn't drink, I had zero problems with other people drinking. I'd go to the bar with people, no problem. Just a personal choice.
But drinking is a social activity. It's got a lot of vibes, not a lot of rigidity. And some drinkers, when out drinking, find that someone who isn't drinking can ruin the vibe. I found that a lot of people who I was okay hanging out with while they were drinking, weren't as okay as having me hanging out while they were drinking.
Enter Liquid Death. Now others feel like you're fitting in. Seems like you're having a tall boy just like everyone else.
Furthermore, since this is now A Thing, if you want to go out, but don't want to drink, it's nice to know that it's gonna be accessible. I was out a few weekends ago, one of the trio was done drinking, but the other two of us weren't. It was nice to be able to buy them a "drink" too, they could get started on re-hydrating immediately. I bought a Liquid Death over this past weekend, when I was out a bit early, didn't feel like having a drink, but did want to support the event I was at buy buying a drink.
Yes, it's "irrational." It's really about human interaction. Which has its own logic.
Because we are all basically apes in clothing and obsessed by status. If you can convince someone that something will make them cool/desirable/higher status, they will buy it, regardless of what it is. Even a $2 can of water. Why do you think people spend fortunes on Lamborghinis, that are objectively shit cars for anything other than showing off? Or Rolexes, which don't even keep time very well?