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I agree that K doesn't like to play against his former players or assistants. But suppose VT wanted to hire Capel or Wojo; they are willing cough up an offer of $1 million per for a four-year contract.
For your assertion to be true:
(1) K would have to persuade VT not to make the offer to a K "disciple." Uhhh, not likely.
(2) K would have to persuade Capel or Wojo not to take the job. Why would they listen to him on the basis of loyalty? They wouldn't, but they would listen to him that it is a lousy job (I don't happen to agree -- see below).
Thus, I don't think even K has the sway to avoid current or former assistants becoming ACC head coaches.
Virginia Tech is a potentially very good job; it's in arguably the strongest basketball conference -- about as good as the Big Ten and much bigger than the Big 12 ("Ten" but the name was taken). Jim Weaver, the former AD, fired Seth Greenberg after his top assistant left and took a lateral to Clemson. Seth was obviously on thin ice, and Weaver seemed unwilling to let him rebuild his staff with expensive guarantees when he wasn't likely to remain very long. And the other thing: how would you like to supervise the always carping Seth?
Weaver retired in November due to Parkinson's Disease. Whit Babcock was hired two months ago from Cincy. He evidently believes James Johnson is a weak coach, and he thinks he can do better. I find it hard to disagree, given the Bruce Pearls, Jeff Capels and other such candidates. (And also, the buyout is probably pretty small, as this is Johnson's first HC job.)