Not really surprising
I would suppose that the Marines started their approach of the game by implementing the same tactics and behavior that they use in real life, meaning keep your head down, save your ammo, short bursts and all that. The Marines are professionals, and approached the matches by identifying primary and secondary targets, setting their well-known tactics in place and following them religiously.
Whereas the geeks went for a par the course game, guns blazing, bunny-hopping and grenading like mad, running willy-nilly all over the place without care for tactics or strategy, jumping in the middle of Marine squads with a detpack to take 'em all out and up the kill count, no matter that they die in the process.
So I am not surprised to learn that the Marines had it a bit hard in the beginning, nor am I surprised to learn that they eventually evened out the score.
As the matches progressed, the Marines certainly learned that, in the game, the geeks do wierd, even stupid things that no sane soldier would ever dream of trying in RL, and adapted their mindset to it. They most probably had lots of fun gunning down the bunny hoppers, like any sane person would. In the end, they evened it out because teamwork and strategy will win over l33t solo skllz any day, and the Marines KNOW teamwork.
The geeks don't, and most likely never will for the most part given the society we live in today.
So yeah, it must have been lots of fun all around, and lets not get all hot and bothered over a few snide comments on either side. Let the geeks think they actually won. Nobody ever looks at the death score, only the kill score counts.
I play a lot of shooters, my current favorite is BF2. It's fun, but if there is one thing to learn from these games, it's that a battlefield is murder, pure and simple, and Justice is on holiday far away. While I have fun shooting pixels and gunning bots or other players, I always realize that, were this a real battle, my life would be hanging by a thread like everyone else's.
It is a frightening thought.