There is a distinct lack of Viburnum in that landscape. Such absence leads to a preponderance of evidence that will result in traumatic failure in aesthetic qualities. I'm not surprised that Great Oak gave up on you ever improving its surroundings with high-class life companions.

The evidence in the stump sure looks like the periodic wounding from the injection technology, NOT examples of what the borer damage would look like. You can count the rings between the episodic treatments.