They fucked up.
The terrorists were only supposed to go back in time 6 years.
The bald black guy with glasses explained this in the pilot.
Their leader, played by Stargate's Tony Almendola, didn't arrive with the core of the cell.
They think he's dead.
Part of the fuck up.
But it's more than possible, that there wasn't a fuck up.
The general just lied to his troops.
Fearless Leader is in 2012 for a reason, and he's totally under the radar cranking out the evil unopposed.
But the troops?
They don't have a plan.
They just want to go home.
No matter the cost.