Why is that gravity is weak at the quantum level?
Gravity is always weak. Why? We don't know.
It just happens to be the most important force for astronomic objects as gravity has no opposite charges, so more mass always means more gravitational force.
Aren't there some explanations? Or at least theories that TRIED to explain this?
There are some ideas, but not in the way you would say "oh, it is obvious gravity is weak!". This is known as the Hierarchy problem.
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