"Mike Tyson ironically, is a supporter of Eastern MA altough he doesn't show it and the tenets of concentration."
lol.
I sure did not know that,nice point though.
I know he once went to check out an aikido dojo while he was in Japan.He trained a bit I think,he threw a punch at an instructor and was pinned/locked in no time (there is footage of this,I think)
Not that they would have been brawling of course.
"but why do most of the martial arts learned these days originate form eastern asia?"
As previously said,this is a small misunderstanding.
When one thinks of martial arts,it is very usual (and maybe logical) to think of Asian martial arts (this is how public knows them)
Most likely there are legitimate western martial arts though.
When we think of western arts like boxing,wrestling etc. (always remember that terms like "boxing" are very common in Chinese MA) we will notice that they are "simple" if compared to a lot of philosophical,highly refined eastern arts which stress daily life in it´s many forms besides combat application (Possibly most important thing considered in budo no kokoro/Japanese martial arts practice is that of educating/raising ppl)
One could disagree with this of course,but those are more like martial sports (western arts mentioned above) than martial arts in different sense.
When you say that most of them come...
well there is some truth to it.Chinese have the longest war history there is and probably the largest number of martial arts styles (this is for Chinese,but consider the civilization and it´s influence on other countries surrounding East-Asia)