[Lotrelf]

I was thinking the same. When I read: "The Ainur are the offspring of Eru's thought." I felt does that make Eru a flawed "character"? He is the creator of Arda. Melkor being the the offspring of his thoughts, means He also belonged to Eru. Or Eru created him purposefully, perhaps. The purpose of creation of The Dark Lord meant, that to exist good, there should be evil. Otherwise all the words we use to express goodness will have no meaning.
Eru cared for Arda, and so did Valar. They did not have to directly come and do the favor to the Children of Iluvatar.