It usually takes entire icebergs calving off to produce such seismic events and intense monsoons to create such flooding.
It seems that past history (especially recent) will not be a good predictor of future events.
While I'd wait for confirmation about the cause of this specific incident, the point you seem to be ignoring is that, due to climate change, events that would have been considered "black swans" historically will become more and more common, to the point that they are expected to occur.