While it could be friends/gf-wife, it may also be the fact that he'll be at a school with less competition and nearly zero pressure if he fails. Even though Helm hasn't been as good as we'd liked to have seen, he wasn't ripped apart by the fanbase. Duke has nearly half the enrollment we have and is a MUCH smaller environment and camps as well as one where there's still zero pressure on players and the team. They're just happy to finally be winning. So I can see how it could appeal from what we've heard about Helm.
It's easy to get lost at UT/grow isolated but Duke is much, much smaller. And let's be real, he has a much better chance of being THE starter and state @TE there with Wolf stealing his thunder - few will admit it but even guys like Helm have egos.