Yeah; I should have said no one has a compelling proven explanation. There are a lot of theories obviously. This article goes into a little bit of detail about it, although in my opinion is proffering its "death by a thousand cuts" theory without that being the consensus of the scientists i.e. "yes this is exactly the combination of factors responsible and they are all significant, we are confident." It's more just that things are collapsing too completely and quickly to even be able to coherently study for root cause(s).