There's an interesting parallel between the concepts of the Valar and the native gods of the germanic people, who Tolkien knew of quite intimately with his love of ancient germanic poetry.  The germanic deities were very hands on in the creation of the world, and the life on it, but then left it all how it was, very rarely attempting to guide or take part in events.  In a similar way, The Valar didn't take much part in the events of Arda, even in the most evil parts of melkor's plans.  It took the death of Mithrandir in the 3rd age to return to Valinor and point out to the valar what was occurring.  And even then, their response was not to interfere themselves, but to return Mithrandir as the new leader of the Istari, allowing him to make influence himself.