When the Black Order's Bio-Warriors reached the world barrier in sufficient numbers, tiny, unstable cracks appeared in the barrier around the Journey to the West World.
To the Journey to the West World, the Black Order were invaders from beyond the heavens. Naturally, it resisted them, keeping them from entering and harming the beings born within it.
But these invaders were outside the world, not inside it. The world's power could not erase them; it could only defend against them.
If Hongjun had already merged with the Heavenly Dao, he would have had all sorts of ways to deal with them.
Unfortunately, the Heavenly Dao, a Gaia-like consciousness, was not that intelligent. It could only resist passively.
And so Thanos's psychic power slipped through those cracks into the Journey to the West World.
The process went smoothly. The world's consciousness seemed exceedingly weak, and he encountered no resistance.
Then his psychic power began scanning the entire world.
A moment later, a sharp glint flashed through his eyes.
"Interesting. Very interesting..."
From what he had seen, the Journey to the West World was the site of a struggle between a man and heaven.
The man was Hongjun. Heaven was the consciousness Pangu had left behind.
After Pangu created the world, his body became the world itself, but his consciousness remained and became the Heavenly Dao.
Hongjun was an outsider. To become master of the world, he had embarked on a long campaign to wear down the Heavenly Dao.
And what was the Heavenly Dao? The collective consciousness of all living beings.
Weakening those beings was therefore the best way to weaken it.
A look through history showed that the general level of power in the Journey to the West World had risen to a certain height before beginning a steady decline.