Unless this woman is like 6'5" or taller, the first news org that got a hold of this story definitely mistranslated "Jin" (斤) as kilograms. Most chinese women are pretty short and it seems believable that she was like 5'2" and 300 jin, which is 330 pounds.
Hell, if she self-reported her weight as 300kg, it's quite likely that rather than lying about it, SHE made the mistake of thinking that jin and kg were the same unit.
Anyway, the thing that killed her was not her fat, it was literally the quantity and pace at which she was eating. She wasn't digesting her food fast enough, so one of her long livestreams of constant eating caused her stomach to literally rip open from the pressure of the food in it. She was a fat girl for sure but she was nothing like the long-term grazing gigawhales we have in America lol