It has always been a mystery to me as to why Eru didn't intervene to stop Melkor and Ungoliant from destroying the Two Trees.
I don't think it is plausible to say that he was not aware of what they were doing while they were doing it, that is to say that he could not see through the cloud of darkness that had been put up around the Two Trees while they were being destroyed. Moreover, as soon as he saw them approach the first tree he should have hit them both with huge bolts of lightning or some kind of power.
So, why didn't Eru stop Melkor and Ungoliant from destroying the Two Trees?
Was this ever discussed with Tolkien and did he offer an explanation for this?