Why has apple tree died? Is it old age or is it disease which could transfer to other trees in the garden.

In time all trees come to an end, tho there are factors than can cause this such as lack of or bad pruning, infection or disease and not treating it in time! Having trees at a base of a heap of grass cuttings or compost heap does not help as acids from the decomposing waste are taken in by the tree and in time kill it. Wind damage, sometimes the tree becomes unsteady and roots are torn allowing space for rot and disease to attack, old age is a factor too Best Paul

This tree could have been pruned badly in the past,if the branches had been cut horizontal instead of on a angle it would allow water to soak in to the tree which in time would cause the tree to rot and die

If you have had the tree badly ruduced or pruned that can tent to kill an apple tree or even reduce the fruit it also could have a tipe of fungus best get it checked

Defo had a bad prune or reduce will cause it or just got too old