Yes.
Part of it!
You have to understand: Earth itself did not belong to the Marvel Universe.
Earth's predecessor was Midgard—the Midgard that belonged to the World Tree Universe. Before Midgard fell from the World Tree Universe and curled in on itself to become Earth, it had already attracted the attention of the Marvel Universe itself.
The way civilizations interacted with one another followed the dark forest model. If even civilizations were like that, how much more so the universes?
The way universes interacted with one another also followed the dark forest model.
Except...
Universes generally would not act against one another lightly. And when they did, most of the time, they stopped after merely making their point.
Before Midgard fell and curled in on itself to become Earth, the Marvel Universe was naturally delighted to gain another life-bearing planet within itself.
So delighted, in fact, that the Marvel Universe used this opportunity to tacitly allow Odin to anchor the unstable World Tree Universe—now deprived of Midgard—within his own universe.
Chthon was one of the earliest deities to appear on Earth.
At the same time...
Chthon was also the source of all dark magic. The Dark God Book he had once compiled recorded all the dark magic he knew, as well as the magic he did not yet know. When he was forced to leave this universe, the Dark God Book allowed him, despite being in another universe, to maintain contact with this one.
As for why Chthon had been forced to leave...
In official terms, Chthon's era had already passed.
But if one put it more bluntly?
Chthon was arrogant and wild, regarding every living being other than himself with contempt. Dark magic required test subjects—everyone knew that.
So...
To avoid being killed by the other gods joining forces