It's trying to balance for the majority of the screen. Since most of your video is of the inside of the car it has gone for that. You can try repositioning it to see more out the window next time.
I don't know what settings they have, but you might also be able to make it work on the focal point, then all you need to do is get the outside of the car in the center of the screen for more magic. Either way, its 1 or the other really, if you get good outside, inside will be dark.
Looks awesome fun either way!!