Well. The Revengers are still alive...and I thought Lord Mar-Vell had killed Scarlet Witch during issue 5 of the Thanos Imperative?
Nothing stays dead in the Cancerverse, hence the point of the universe. Mar-Vell and the Great Old Ones were defeated by Death, so it's reasonable to assume that their mastery over death faltered when 616-Death made her appearance. And once she left, the lack of a death entity probably allowed everyone to revive again. You can use "because reasons" for everything else.