I have to wonder: would the suicide have been prevented if chatGPT didn't exist?

I'd say yes, because the signs would have to surface somewhere else, probably in an interaction with a human, who (un)consciously saved him with a simple gesture.

With a simple discussion, an alternative perspective on a problem, or a sidekick who can support someone for a day or two, many lives can and do change.

We're generally not aware though.