[Ithaeliel]

In my personal opinion, the Valar would not have needed to intervene had not certain circumstances arisen.

I suppose that once the advisors arrived in Middle-earth and began their task, the Valar put their faith in that and turned away from the matter. Yet Saruman joined forces with Sauron, strenghtening the enemy and weakening the Free Peoples. I suppose had not his happened, there would not have been as many deaths and things would not have gone so awry. Saruman was meant to fight against Sauron, not with him. I suppose the Valar might have been a little late in seeing that. Maybe they just didn't find it a large enough matter. I'm not sure. Good question, though.