Lich Transformation questions

[the Jester]

"Wait, you want your character to become an insane, evil, Orcish-worshipping npc? Okay, if you really want to..."

 

[Mirtek]

Hmm, I missed that part. Why does he not benefit? Thanks.

Because as soon as he reaches 0 or less he crumbles to dust, doesn't matter if he would have a dying threshold of -100 hp and not failed a single death save, it triggers as soon as he is at 0 or lower