Confess!

The people of the world could not see the other two Divine Comprehension leveler like they see Death Monarch.

But just because they could not does not mean they could not sense it. Anyone above Seed Forming could trace the source of energy 

Other than the Turbulent Sea where their Divine Sense is heavily distorted, the rest of the world is still somewhat possible for them to feel it

And they know from the power unleashed that the only people able to unleash such power that could affect the world to this degree is none other another Divine Comprehension leveler. 

Jean uses the power of Time, the Space was affected and his power spread all over the world. 

Hikigaya conjure up demons and unknown beings, parading in the sky, demonic energy fills the sky and rid of the coercion of the heaven, like a battle between demons and gods. 

Their auras were equally terrifying, morphing their surrounding unconsciously.