I came across a subtle usage of “ensure” in this context，
What is strangest about the case of China’s worst diplomat is that he was given this fateful mission at all. For he had bungled things before.When he managed a river, deadly flooding ensued. He was fired—then given another job. When he oversaw trade with foreigners in Tianjin, an important port, there was a horrific massacre of French clerics. He was fired again—and promptly sent to France as an imperial envoy.
My question is how to understand the exact meaning of "ensured" here in the context. "Ensure" means "make sure that something happens or is definite"(according to OALD).
The sentence then can be paraphrased as "when he managed a river, his management made sure that deadly flooding happened."
I am not sure if it means "whenever the man managed a river, it was bound to flood" or "the man had once managed a river, and a deadly flooding followed in defiance of his management".
How to understand the meaning of “ensure” in this context？What exactly is the author's idea indeed?