interestingly it may actually be related to writing

right hand is controlled by the motor system in the left hemisphere which is the rational, forward time processing part of the brain

some recent studies (with brain scans and reading/writing exercises) have shown that right to left scripts engage the right brain (controlling the left hand) and weakens the capacity for language and reason overall

just look at the middle east, what direciton do they all write?

just as you leave the ink behind you as you write right handed left to right, to do that right to left you need to use your left hand and that trains part of your brain that is not suited to language, but instead is the part of our brain that does predictions and creativity, negative space, and so on

pretty sure that the people of the fertile crescent tried to spread out across into europe but funny enough the right to left languages did not

this is probably because right to left makes for overall less rationality and capability at warfare in general

it may seem silly but if the right brain is not made for sequential logic, but instead is better at telegraphic and holistic, visual thinking, then it also means less capacity at planning and strategy

there's probably more things involved in this but i'm sure if you tae that first thought (about the difference in brain hemisphere control of the hand) you might see a lot more things that are disadvantaged by using a left to right script, and left-dominant swing of the stick/club/sword is probably part of it too but the picture is probably a lot bigger