Isn't Haki tied to will power? Maybe it blooms because when faced with uncertainty, uneven odds and impending death, one still grits through with determination to win and protect their ideals. Real life people who struggle to carry a paper bag of groceries have reportedly lifted cars to save their baby, maybe something like that for those that don't succumb to acquiescence.
I’m just explaining the whole Haki ending doesn’t necessarily mean it will end sometimes based on story logic with haki blooming