A deity coming over would not be able to fight those plants, and even if many deities came, they might temporarily suppress the plants, but a unified opinion within them was unlikely to form. And given the situation at that time, no matter how things ultimately developed, as long as the invading deities couldn't unify their opinions, the situation would eventually progress to the state it was in, which wouldn't be surprising.
And indeed, at that time, the deities ended up fighting amongst themselves.
No matter what, they couldn't allow any other deity to obtain the deityhood, so even if they had acted with great harmony before, the moment they saw a deity attempting to seize the deityhood, without exception, all the other deities chose to attack that deity.
The result...
