Its because you havent read the bible well, those were hybrids (genetically modified, not humans anymore) because they were giants(nephilims) and offsprings of giants(from humans who cohabited with the fallen angels) . Because of this modification, these people were bent to evil and could not be redeemed. So God wanted to preserve the pure breed through which the messiah would come.
If you honestly believe that the universe was created for man to rule, then I'm sorry to tell you that you are living a well articulated lie.
And until you are truly stable enough to see religion for what it is, then you will miss out on the poetic beauty of science, math, music, art and geometry.
Half the Bible is deeply immersed in paganism, study occult my friend.