The main factor that enabled such a crazy clear was the use of creative game mechanics to boost the damage of the Corruption ability Twilight Devastation
, which unlike many other Corruptions, scales exclusively from your maximum health.
What made such massive Twilight Devastation hits possible was the stacking of the minor tank Azerite Essence Strength of the Warden
, which increases the health of all Tanks at the raid by 3%, stacking with itself. With all 30 tanks in the raid using the Azerite Essence, plus many Stamina-increased items, many of the tanks of the run were stacking millions of health, and by proxy, dealing millions of damage every time they got a Twilight Devastation proc. They were also requiring other items such as Vita-Charged Titanshard
equipped, to try to fish for as many Twilight Devastation procs as they can get.