Hard to say without a lot more information. A photograph MIGHT help, or any words you may have about anything else you can see on the tree - maybe coral spots, or sunken areas in the trunk, oozing from the trunk or branches, rotting at the base, infestation of scale, that kind of thing.

and at this time of year I would nt expect any leaves anyway. wait and see what happens this spring. Did the trunk have any toadstools growing from it? Scrape a little bit of bark off, is their a layer of white fungal fibres which smell strongly of mushrooms? If yes then it sounds like honey fungus, which blossom trees of the cherry/plum/crab apple family are susceptible to. It seems a bit young to have died of old age. So check for this fungus.