What we think of as normal and obvious is only that way through decades of experimentation.

If all you had to do in a game was move and nothing else, then it would seem desirable to choose four keys where you could use four fingers all at the same time. An arrow shape like WASD doesn’t do that because your middle finger does double duty for both up and down.

So, having decided on one fingrer for each direction it makes sense to use two hands. And using two hands it makes sense to spread the keys out so your hands can be apart on the board, not cramping each other.

It seems terrible in retrospect, but you can appreciate there must have been some logic behind the choice at the time.