Regarding death feederism in general, I also don't remember it being a thing until the 2010s. There was a podcast once that featured mostly gay male gainers called The Gaining Life. The majority of them didn't speak much on their weight issues specifically or their desires to or not to be fat, just how they found the community and when. One guy, however, I want to say it was Fatfatplus, but don't quote me, said something interesting. He mentioned that he knew guys who were looking forward to health problems and they wanted heart problems because that would somehow make them feel validated. It was just a throwaway comment, I forget who he said it to, but it was the first time I'd ever heard of or contemplated such a thing. I think with increased exposure of a kink comes more extreme ways of experiencing it. As a result we have people who see the exaggerated porportions of the classic fat art and think they can make it real, with complete awareness of the potential side effects and consequences such decisions can have. In truth almost no one who attempts such a thing intentionally ever achieves their goal of literally dying from being too fat. Those that do are almost exclusively medical/mental health cases which resulted in extreme and crippling food addiction.
I think the desire to achieve death by feederism is rooted more in the desire to have the fantasy image of complete freedom and control over one's life. In fantasy terms, being completely immobile obligated others to do your bidding: housework, cooking, errands etc. It implies a level of financial stability: money to throw away on ungodly amounts of food, paid off house or consistently paid rent, vehicle to transport person and food, and maintenance on both. It guarantees a lifelong commitment beyond the obvious: a feeder partner is stereotyped as only wanting the largest feedee with the biggest appetite, and as long as they have it they will never leave. And it also demands attention: on top of having literally everything done for the feedee, they are also going to see doctors, presumably frequently. This would cause emotional upset, sympathy and pity from others, and a general ability for either intense enjoyment at causing such emotional intensity, or manipulation to make it continue or create the desired reaction.
In the end I think most people who claim to want to gain until they die really want one of two things. Either they want control and security in every aspect of their lives, or they want power and control over others. Both dynamics have played out multiple times on 600 pound life, intentionally or not.
That said, people who weigh 800+ pounds are exceedingly rare, even in the realms of reality TV and internal medicine. And, to my knowledge, it is really REALLY hard to purposefully eat enough consistently enough for a long enough period to get that huge. Which is the most likely reason it is so rare in real life.
I found the podcast in the waybackmachine, if anyone is interested:
archive.org/details/TheGainingLifeAs mentioned, none of it is particularly illuminating, but it is an interesting snapshot of what feederism was like in the 2010s, and reflections from some of the people who were there in the early internet days. Warning: some of them didn't have the kink and were in it for acceptance before before fat acceptance was socially acceptable. Some episodes go more in depth than others, food preferences, eating a lot how and when, those sorts of things. The majority of it is centered on the individual's self perception, and isn't really a how to guide or instruction manual of how to get fat. Some episodes never mention kink or intent but are about physically living as a huge person (superxlchubboy's is worth listening to if you think you want to weigh 800 pounds).
