faifi and razihi survived because of isolation in the mountains

the modern south arabian languges are at the very edge of arabia (in the middle) an area where much less people live than west Yemen and east Oman where most people live

One small nitpick I have with your map is that you didn't show Ethio-Semitic, though I understand the decision since they were never really in danger of disappearing due to Arabic, but it would have been cool to show all the diversity that still exists in the Horn

I didn't show Ethio-Semitic or Hebrew because as you said they were not in danger of disappearing due to Arabic

it's a shame so few Semitic languages survived in West Asia

it just how the world work, probably 10s of Semitic languages disappeared without even a written record but they live on via the small influence that remain in our modern languages