Obviously Peter Thiel needed her to make whatever concoction he’s brewing.
But seriously, when you’re that old, each day is (for the lack of a better word) a blessing. I’d bet she probably had several underlying conditions (what 96 year old has no health issues?) that ultimately killed her. But, for everyone, death is in fact inevitable.
She definitely did, even if the palace was and still is coy about them. And her decline in the last 18 months or so (Philip's death being a major factor there, of course) was evident and undeniable.