Star Wars: Battlefront - How is this possible?

In case you guys don't remember or don't know, the game was filled completely with walls not even here or glitches all around maps.
the biggest glitched was the death star, as you could go through 2 walls, one allowed to snipe an entire corridor, the other one allowed you to jetpack all around the map and there even pyramids in the death star.
The one on Tattoine has also a lot of glitches, up to 3 parts where you could go in the walls and the famous infinite death glitch.

spppppaaaaaAAAAAAAAAAAAAACCCCCCcccccccceeeeeeeee 'passes by'