I'm gonna go with PIS or plot induced stupidity. We probably lost just because they say we did. I could see how we (2014 humans) couldn't stand a chance against the covenant. They had multiple planet invading fleets and tanks(other shit like that and lots of it) and multiple planetary species working together. The fallen and hive? That's a little of a stretch to me. Bungie just needs to show something to make us fear or hate the aliens in this game. Right now they just look like target practice for guardians. 3 guardians invading a planet, taking out their orbital communication jammers, and smashing through their army makes them look weak as fizuck.