External vendor (they went el cheapo, didn't vet properly, didn't communicate risks, etc..).
Software bug not under their control (they didn't perform a proper FOA).
Hardware failure (what, you mean AI didn't predict it, and could not reroute/resolve it quickly?).
Sabotage (blame it on disgruntled employee).
Other - get creative here :).
We all know VZ leadership will not accept responsibility.