The fact that some of the world's most annoying people (eg Musk, Thiel) are throwing money at this should clue you in to the point: it is about maintaining the current economic structure and, in "ideal" world, living forever (eg transhumanism, mentioned in the article) to "enjoy" it for the very few on top.
Honestly I draw some comfort from our own mortality because the very worst people ultimately die too. If we ever achieve effective immortality, part of me believes that could be truly catastrophic for society.
> We can now begin to see how longtermism might be self-defeating.
Karl Marx talked abou tthe contradictions inherent in capitalism and that it was ultimately unsustainable in the 1840s through the over-accumulation or cconcentration of capital. Marx predicted a response to this being a revolution by the proletariat, which has thus far not come to pass, but the tool for squashing uprisings has been and continues to be fascism.