after Macbeth learns that Lady Macbeth is dead he says life is a tale/told by an idoit, full of sound and fury, signifying nothing." How is this different from his attitude earlier in the play?

Given the great love between them, his response is oddly muted.

hat the audience realises how completely his wife's passing and the ruin of his power have undone Macbeth. His speech insists that there is no meaning or purpose in life. Rather, life "is a tale / Told by an idiot, full of sound and fury, / Signifying nothing." One can easily understand how, with his wife dead and armies marching against him, Macbeth succumbs to such pessimism. Yet, there is also a defensive and self-justifying quality to his words. If everything is meaningless, then Macbeth's awful crimes are somehow made less awful, because, like everything else, they too "signify nothing."

So this shows that his attitude has changed due his wife's downfall. Giving us an inkling that Lady Macbeth controlled him. Him now knowing that she has left him to his own fate and that he can't decide what to do on his own.

It is all so fleeting, and individuals spend their brief "hour" of life full of sound and fury. For what? Against whom? In the end, none of the fury that consumes so much of life amounts to anything.

Macbeth realises that he has wasted so much of his brief life (and, by extension, all of us do as well) and that it has all proven meaningless in the end. So it's as if his 'evil and remorseless' attitude has changed to a saddened end to his wasted life.