We see this symptom fairly often, though its exact cause has yet to be confirmed. Our primary suspect is a different root rot, Thielaviopsis, to which various holly species (plus assorted other species, mainly bedding annuals) are vulnerable. Like the other root rot pathogens, they tend to be opportunistic, infecting plants already stressed by something in the growing environment, either soil that is too wet or, as noted in the linked publication, not acidic enough (especially for acid-loving plants like hollies). The organism can exist in soils for some time without causing disease if the host plants are growing well. (Their ubiquity is another reason eradication using a fungicide soil drench is not practical to try, as the soil could be recolonized at any point by this or similar species in the future.)

Whatever the exact cause, unfortunately we have not seen Inkberry recover from this degree of damage, so removal and replacement is recommended. You could try growing Inkberry again there if the site appears to be suitable, though using a laboratory soil test to ascertain acidity level (pH) may be useful in case it needs to be adjusted. Sometimes, soil near home foundations can be closer to alkaline due to leaching from the concrete. The amount of summer sun, soil wetness or drainage, space available for plant mature size, deer browsing risk, and soil acidity are all factors that would go into choosing an alternative if you wanted to try another species of shrub.

Miri