In newtonian gravity, there's a very simple geometric reason why the force of gravity is one over our squared. In general relativity, that's almost true but there's a new effect that comes in - and it could be related to black holes. The gravitational field in newtoniangravity is not a source of gravity, whereas the gravitational field in generalativity is. So when the gravitational field becomes relativelyt on in general relativity, we expect it to deviate from the newtonian prediction because there's an extra source of gravity.