mallus apple tree

The first question would be when it was planted. If it's a new planting it may take some time to establish. It's common for trees and shrubs which are in difficulty to make lots of blossom in an attempt to flower and fruit before they give up the ghost! When you say the leaves looked dead, was this after they came into leaf in the spring? If they have 'picked up' in the sense of the tree making new leafy growth, you can be hopeful as it sounds as if it has now established itself.
Just keep it watered until the autumn and after a normal winter it should come back unless it is seriously diseased in some way.