I hadn’t heard of that one before, and I was surprised it missed it, Wiki says it won two (2!) Eisner awards. Did you like the story?
As for why Batman is still alive - that’s just something you got to live with as a comics fan. The rules of the genre allow way more “anything goes” than other media, like novels or TV.
You could also ask why there was a Batman story set in the 19th century (Gotham by Gaslight) or in the middle ages (Batman: Gothic) and on top of THAT, there’s all the “Elseworlds” stories that are like an alternate universe (DC calls it Elseworlds, I forgot what Marvel calls it).
What’s more, we’re gonna see Batman die (more or less?) pretty soon in the on-going storyline “Batman RIP” even though we KNOW that he’s going to be alive in the near and far future nonetheless.
So, the way I see it, look at it from a graphic perspective, not a textual one. Comics transcend the mere text, they’re not linear by definition. When you read a book, you read one word after another, but when you look at a page in a comic book, all the panels, all the images exist at the same time, that’s a basic trademark of the MEDIUM “comic book”, that all the images exist at the same time, whereas in a movie for example, you can only see one image after another.
And then when you take that insight and transfer it to the comic book character Batman, maybe you’ll see how he can exist at different places in time - he’s not linear, just like the comic book itself.
And THAT is why comic book characters are best appreciated within the framework of their original medium, the comic book, and not when they’re taken OUT of their medium and transposed into another medium, like movies. That’s one of the main reasons, in my opinion, that superhero movies so often fall short.
Does that make any sense?