But why did the terminal choose those keys? Most games have chosen an up-down combo that are up-down from each other, rather than right-left.

The thing about ASCII Control characters doesn't quite map to left-up-down-right, and even if it were part of the answer, we could ask again: why were those characters chosen for those control-roles?

And the reason they didn't was that they evolved from typewriters that relied on a forward/backward spin to move up and down (except for the carriage return lever). We're lucky that the original terminals didn't have a scroll knob on the left and right of the machine to move up and down and a lever to move to the next line or we would have been stuck with that concept for years and the laptop may not have been invented because the knobs and lever would have required some elevation, which means the whole thing would have had to have been bigger.