quote pasmon

He looks like a treasury nut who has no skill of leader-ship or even communicating to his juniors as director.

That's pretty much it. He was the GDI treasurer, so he was meant to mostly be in charge of sums. But when the Philadelphia was destroyed, everyone above him on the chain of command was killed, so he was left as the highest ranked director. Whether he is any good or not doesn't matter, he was left as the one in charge of GDI, and everyone had to follow his orders. Prior to all this, there were competent leaders in charge of GDI, and they'd done a good job of destroying Nod on the surface. Unfortunately, they once again assumed Kane was dead and that the Brotherhood was now nothing more than a few splinter groups. How foolish to let their guard down.