Die back from pathogen can be rapid and often totally kills a tree. Hopefully it’s spotted before travelling to the main trunk and can be removed or the treee compartmentalises the affected branch. Sometimes I don’t catch the disease early enough to remove the affected limb and if in the main trunk, will cut the tree down to a stump above the graft. Here’s some pictures showing a tree just starting to bud back, another a little further along and lastly, one that had this treatment a few year’s back. They have all been saved and will recover.