The Silmarils

[Aredhel Idril Telcontar]

he could of given them to Ungoliant if he wished them destroyed, but instead he destroyed her,

He did not destroy her, she was much stronger than him by that time.
Morgoth did overthrow the Noldor and he did seem to be winning, but he might have overestimated his defeated enemies.
Being evil, he did not know forgiveness, however, so it is very unlikely he would suspect the Valar to help them.
Then again, wouldn't he suspect the Valar wanting to be rid of him [img]smilies/wink.gif[/img]?

-Aredhel