Sounds like it was well planned.
Remember the articles a few years ago about how the power system was very vulnerable? Well the towelheadjihadis read the articles too.
They knew that long before those articles came out. They leveraged sabotage of the power grid to an extreme degree in Iraq. There was many areas of Iraq that was without power for years even with the full US military guarding the systems with the help of drones and everything else.
The jihad activity and its destructive effect on the power grid in other countries is what prompted those articles if they ever turned to such methods in the US. If they could do that much damage to a grid being guarded by a full class military, then think of what they can do to a totally unprotected one here.