This one has been a long time coming. VT has felt like the favorite for a while (both from the inside of the program and the outsiders' perspective), and this is simply the culmination of a process during which he was just trying to find the right time to make the call.
The VT staff thought it was likely that he would commit when he visited in April for the Spring Game. Seeing him as an outside linebacker/hybrid DB rather than an inside 'backer (where he was previously ranked on Rivals), they wanted to be sure he was properly evaluated at his future position prior to making a commitment. That position - a hybrid outside linebacker who can be athletic enough to drop into coverage, but may be big enough to rush with a hand on the ground in passing situations - is a really good fit for him. Tisdale sometimes plays safety and often plays a pass-rush role for his high school team, in addition to the standard linebacker duties.
Although we reached out to Tisdale in the days leading up to the aforementioned visit and he reaffirmed to us that a commitment wasn't in the cards for that weekend, it was apparent that it was only a matter of time. The Hokies didn't slip up at all in keeping the pressure on him, wanting to ensure that they sealed him up instead of resting on their laurels and missing out. That obviously came to fruition today.
With Tisdale in the fold, that's another good friend (though not as good as Tre Turner) of KJ Henry's in the fold. While the five-star defensive end isn't going to make a decision simply because others in the class - top recruits rarely do - every little bit helps in a hotly contested recruitment. Henry himself said that every North Carolina commit to the Hokies helps their cause just a bit, and when that's a player he already knows well, it can only be a boost. None of this is to say Tisdale's commitment is meaningless other than as a boost for Henry, but it's another positive factor.