Fortunately, Oak Wilt is quite unlikely, as very few cases have been detected in Maryland, and all were in the westernmost counties. The symptoms pictured are not distinctive to any one pest or disease, and it's probable that several stress factors or injuries (storm damage, perhaps) overlapped to push the tree over the limits of its tolerances. Symptoms of tree decline often don't begin to become obvious until months or even years after it begins, so while dieback can appear sudden, a tree can actually be in decline for a while leading up to that point.

There are a plethora of reasons why trees decline and die, and making a diagnosis once the symptoms are advanced can be challenging if the original symptoms became obscured by other conditions. Drought and excessive rainfall, which we have experienced in recent but different years here in Maryland, could have damaged roots, resulting in canopy dieback because it can't stay hydrated. Stress can make trees more of a vulnerable target to wood-boring insects and certain pathogens, which infect a weakened plant and then cause its demise or greater damage. We think we see some indication of the presence of Hypoxylon canker, for example, on at least one of the trees pictured, though it's hard to see enough detail. That organism can kill mature trees.

In order to try to determine what happened, or if any conditions in the area might have contributed to tree stress (soil drainage, perhaps), you could have the trees assessed by a certified arborist, including any healthy-looking trees you are concerned about. While arborists cannot treat every condition or reverse tree decline, they can make a more thorough assessment in person than from photos, and can look for indications of specific issues, like canker, borers, lightning strikes, and so on.

Miri