The Nashville bombing is pretty sophisticated for a disgruntled employee type motive
Otoh, it would hardly be a surprise that an AT&T employee would have fairly high level technical skills.
The elaborate warning tends to mitigate against RWNJ politicals. They love to fantasize about killing. It is at the very center of their cultural pathology.
If the perp was in the RV when it detonated it would be understandable that it has taken so long to discover remains.