Evolution.
In a general sense, the word 'evolution' often brought something positive to the planet.
At times, it brought strange yet desirable traits for survival.
Whether it was plants, mammals, insects, or reptiles, everyone got their time to shine. History repeated itself, and the modern evolution was no different.
The oxygen-rich environment favored creatures over plants. As the creatures got bigger, their oxygen consumption also increased. This, in turn, increased the carbon dioxide in the environment.
Plants latched onto it and grew bigger, compensating for the oxygen consumed by the creatures. This circle was mutually beneficial for both the plants and the animals.
It was a delicate balance.
However, not everyone or everything receives equal treatment by nature. Some are favored, some are discarded.
As plants grew, the nutrients in the soil got depleted quickly. Not everything could survive such overgrowth.