I live in Northern California. We have two Japanese maples. Our gardener pruned one of the trees in the early winter, mostly just cutting small branches on one side to prevent the leaves from filling our gutter. The tree is dying now, while its sibling across the garden, which he did not prune, is doing well. He said the tree was probably diseased before he pruned it, and showed me a bad cut at the trunk level. The bark is peeling off and the twigs are either very dry or dead. Unlike the other tree, this one is not making leaves. Is it possible that it’s merely coincidence that the tree is dying, or is he just denying responsibility? This is someone I have trusted for many years and never had a bad experience with him.
While the issue of your gardener is beyond the scope of Ask a Master Gardener, when a tree receives a trunk wound that penetrates the cambium layer it can interfere with the movement of water and nutrients. Since there is no leaf growth, it is possible that the tree is dying but you may want to consult with an arborist before removing the tree. A wound can become a pathway for diseases, insects or decay. If the tree needs to be replaced it is important to provide the proper conditions for growth, to monitor for disease and to prevent hazards that can cause wounds. For ongoing health of your other Japanese Maple and for any replacements, our Gardeners Guide Growing Japanese Maples is a good resource: