Those people died after ingesting impure DHMO, which is 'watered down' by relatively unharmful minerals, making it only fatal after ingesting large amounts. 100% pure, distilled DHMO is actually extremely dangerous even in small quantities, as it leeches essential nutrients from your body through a nefarious process called 'reverse osmosis'.

[EDIT: this is actually not true, according to the wisdom of the interwebs. Thank you, extremely expensive European public school system, for filling my young impressionable mind with this untrue factoid. Nevertheless, the dangers and risks of DHMO ingestion remain poorly understood.]