It was always to be this way, my son. You merely provided the key to unlock this terrible fate. The denizens, and heroes, of Midgard allowed petty differences and petulant squabbles to stand in the way of their own future. There is a point in the evolution of any species where they must discard their tribal differences and unite as one people. One cohesive representation of their world on the cosmic stage. This is the test of all life. To see their world relative to the stars. To finally absorb how meaningless their rage at their brothers and sisters truly is! ... I had great expectations they would. Yet they continued to war over their trifling differences. Combat their only means of solution. Too savage to be allowed to join the cosmic community... and the Celestials deemed them unworthy for it. As hard as it will be to accept it... the true fault lies with men. Ragnarok was their choice.
The heroes and denizens of Midgard were also responsible since they allowed their petty differences and squabbling to stand in the way of their own future as a united people and thus the Celestials deemed them unworthy for it.