A long time ago, there was a river.

This river used to be lush with aquatic plants, and the water was clear. Crocodiles lived in the deep waters; small fish and shrimp hid among the mudflats; deer herds and wild horses drank and foraged along the banks.
Later, the climate changed.
The river grew shallower year by year. There were fewer aquatic plants, and the mudflats turned foul.
The first to leave were the deer herds and wild horses.
They had no sharp teeth, and no thick armored scales. Once the old river went bad, they had almost no advantage. So they followed the distant mist of water and proactively left the riverbanks they had lived on for years, to search for new water sources.
The crocodiles didn’t go.
To the crocodiles, even though the old river had worsened, it still hadn’t reached the point where they couldn’t survive. After all, they were the top predators in this river. They knew every deep pool and every dark current, and they knew when to lie in wait and when to strike.
Even as the water got shallower and prey became scarcer, they could still catch food by relying on experience and strength.
And precisely because of that, the crocodiles didn’t migrate right away.
Their strength allowed them to get by in the old river; it also made them miss the chance to move into the new waters earlier.
By the time the deer herds and wild horses had already eaten richer aquatic plants at the new river and seen wider horizons, the crocodiles were still maintaining their advantage in the old river.
They didn’t fail.
They were still powerful.
It wasn’t survival that they missed—it was a bigger opportunity.
Small fish and shrimp also didn’t leave.
They were used to muddy water. They were used to digging through the silt for leftover food. They were used to betting their luck as the water level rose and fell.
When the water was a little shallower, they bet it would rise again tomorrow.
When there was less food, they bet that the next wave of water would bring in scraps.
As some of their own kind died, they bet that this time it wouldn’t be their turn.
So they kept staying in the old river, fighting and rolling around in the ever-narrowing muddy water, sinking deeper and deeper.
Later, the old river kept going bad.
Deep pools turned into mud pits, and clear water turned into stinking water. Finally, even the crocodiles realized that they hadn’t lost to other crocodiles—they had lost to this river.
So the crocodiles began to migrate.
With the judgment, patience, and strength they had built up from years of hunting, they quickly re-established their footing in the new waters.
There, the water was deeper, there were more creatures, and there were more opportunities.
The crocodiles didn’t come the earliest.
But the crocodiles were still crocodiles.
In the end, only some small fish and shrimp remained in the old river, along with a few crocodiles that truly didn’t want to migrate.
The small fish and shrimp were still struggling in the stinking water, still betting on the next time the water level would rise.
Those few crocodiles guarded the deep pools that were getting shallower and shallower, continuing to wait for the old river to return to how it used to be—
until the next rainy season, when the river became lush again, and the animals came back to it. It looked as if nothing had changed, only that the riverbed now had a dense layer of corpses.