yahweh originally made the messengers of heaven, from of whom are the fallen ones that are called the tree of knowledge of good and evil. however, after their fall, they mixed their seed with every kind. thus the perversion of that which was originally good.
wouldn't the word 'evil' in the verse of isaiah you reference be better translated as 'war', 'calamity', 'chaos', and so on, being self-evidenced by viewing the verse as a whole and comparing the analogies, as, light is to darkness as peace is to war, disaster, calamity, and so on? if not, then would it not have been contrasted with good instead of peace?
neither the hebrew word 'rah' nor the greek word 'kaka' necessitate moral-evil, but rather, disastrousness, hence the contrasting analogies of light and dark, peace and disaster.
it isn't suggesting 'evil' in the sense of the binary-moralcode given to us by yahweh, that of good and evil.
if something was already evil, then there would be nothing to pervert it into.
again, open to correction if i'm in error.