It seemed their plan was working, as soon as they got to the Autobot base, the Combaticons would kill the Autobots there, and take it for themselves. Blast Off knew they could make a communication device from the amount of wreckage, and the Energon from the Autobot bodies would help power it. There was no better way to summon Megatron, than on the backs of decapitated Autobots.