The Old Testament, which was "given for our admonition" even to those who believe in Christ, shows in prophecy after prophecy and event after event that God brings judgment against nations for their sins against His Laws, and often for the worshipping of the demon gods. Knowing the exact causes of particular calamities is not possible for us.
If we can't know the exact cause of the calamity, it's not a particularly effective lesson, is it?
It's similar to a man smacking his wife. When she asks why, he says, "'cause."
And how do we know when something rises above the usual, normal disaster into something that is a judgement on a nation? If 200 people die, is that a judgement or just a tragedy? If there are widespread forest fires, but no one dies, is that a judgement on the nation? Or the nation's trees maybe?