Although both have good scouts into knights options they aren’t exatcly the typical arabia civs. Persians used to be played a lot on arabia before the faster dark age tc (which was added with the release of DE) was removed again. I personally didn’t get it to begin with (I think they were only op in hybrid maps and are still very strong there so they could have removed the wood bonus at the start or something instead of dark age tc) but that’s another topic. It’s just that people aren’t using them anymore on 1v1 arabia. Probably because ultimately their gameplay is rather defensive and the open kotd arabia doesn’t favor that style. They are quite a versatile civ but that versatile only comes in in late game.
Teutons also have quite some weaknesses on open maps starting from mid feudal age, namely bad archers, then no husbandry and in imp even no light cav. This means at some point you usually switch to infantry and siege which also doesn’t fit the open map style of kotd.
Generally, archer civs seem to be less used because of increased use of scouts and skirms. Japanese were popular on previous kotd editions because of maa into towers but you see less towers nowadays. From these 3 we could see vietnamese used most often probably because they have the best (long-term) eco among them and a knight switch makes more sense compared to the other two.
But the tournament is far from over and most matchups heavily favored one player so let’s see how it continues.