The Red vs Blue machinima creates a story-line in Halo that did not previously exist. Many would play Halo multiplayer and just have a good time. This machinima reveals some logical questions about the whole concept. Like they said, the bases are inside a box canyon, outside of controlling that box canyon the bases would be relatively useless, as there is no way in or out of the canyon besides by air.
Then there is a question of what each team is fighting about. If this is really stemming from Halo, then maybe one team sided with the Covenant or Flood. The Covenant wants to complete their genocide of humanity though, so that seems a bit strange. So the only outcome I could see is one of the groups being heretics that sided with the Flood, which was just lifeforms that wanted to devour everything. If this was not the case, with those two massive threats on the sidelines, you would think that the two groups would put aside their relatively minor differences to fight one of the two other groups.
Just viewing this one example can give viewers plenty of other ideas for other machinima projects. Why do battle royales happen? Is PUBG's reward for being the only surviving person or team literally just a chicken dinner, and if so, why risk your life for a chicken? Why do characters fight each other in Super Smash Brothers? These questions are easier to come up with in multiplayer games rather than single player games though, but not quite impossible. In Dark Souls, is it wrong if the player wants to just relax and wait for another undead or ashen one? Would the player just turn into another crestfallen warrior, and be really depressed about their circumstances? The ideas one can come up with machinimas to expand the game's lore into their own head-cannon is quite literally infinite. I find this to show how powerful a medium Machinimas are.