Trees in containers do not "all of a sudden" become rootbound. It most certainly does happen but the process is gradual. It is also extremely easy for a containerized tree to dry out and lack of adequate water can sometimes be overlooked, resulting in a wilting or drying of leaves.

And there may be a number of things going on with this tree that may have other causal agents at work as well. The size of the container could be at issue, the frequency of repotting, the type of potting soil used/drainage and the routine of watering and fertilizing can all create stressful conditions that allow the tree to become more prone to disease issues.

From just this photo, it is difficult to say exactly what is going on. If branches are dying off in sections, then there is some sort of water issue which could include a root rot. Unfortunately not a lot you can do at this point but wait and see. If it is that serious, you will know soon enough -- the decline is often very rapid.

If not life threatening, it could refoliate on some of those branches. And if this happier option, consider repotting this winter when dormant in either a larger container or with some root pruning and fresh, durable potting soil. Or plant in the ground.........moles do not eat any plants or plant roots and do minimal damage to any woody plant by way of disturbance.

Verticillium Wilt?

Verticillium Wilt is a disease that can attack Japanese maples. Symptoms are pretty obvious. In some cases the leaves on a single branch will discolor and die, but do not fall from the tree. In many cases the branch dies completely and should be completely removed from the tree at first sign of the disease.

How do you know for sure the branch is dead? This is how you test to see if a plant, or a branch on a plant has died. Just scratch the bark of the plant with your finger nail. If the tissue below the bark is green and firm your plants are fine. If the tissue is brown and mushy that part of the plant is dead.

Verticillium Wilt is caused by a soil borne fungi but usually attacks plants that have been stressed by other things. Drought, frost, or wet soil.

I would put it in the ground now or put it in a larger pot now. It looks like you may have to break the pot to safely get the rootball out.
I think it's a temporary lack of water that has caused the dieback.
That's a large plant for the size of the pot and it can dry out very fast.
Mike

Moles are carnivores they do not eat plants nor plant roots....Moles would not be a reason to dig up a tree and stick it in a pot....

When you potted it did you use potting soil or dirt from the ground you dug it up from?

Probably drying out in spots in the pot, very easy to do.