The way the whole tree failed quickly, something likely impacted the tree's ability to move nutrients and water throughout the tree. The few leaves/branches that have resprouted will not be enough to sustain the tree. It will likely not sprout much at all next year, if any, and the sections that area dead will remain dead.

Assuming nothing has recently changed dramatically in the root zone (like cutting of major roots or flooding), wilt or root rot could certainly be suspected. They both can display symptoms like this. You would need to confirm diagnosis of this by a diagnostic lab. Note that for Verticillium wilt you will need to send in a very specific type of branch sample, as instructed in the lab link below. For the root rot, you would need to send in a root sample.

Here is a link to MSU's diagnostic lab's website:

Plant & Pest Diagnostics (msu.edu)

Here are links from MSU with more detailed information on Verticillium Wilt:

Verticillium wilt refresher - MSU Extension