Absolutely hilarious to me that Kamala's two most famous quotes, "You think you just fell out of a coconut tree? You exist in the context of all in which you live and what came before you," and "What can be, unburdened by what has been." Are just two completely mutually exclusive statements.
It would have been gauche for them to release a signed statement of his stepdown if he was actually dead, but if he's actually in bad enough condition that he can't appear in public for the forseeable future, it makes sense that they'd want Kamala in as soon as possible to take over the campaign.