Its a recognition by the most powerful country in the world, the US, that Jerusalem is the capital of Israel. Its a slap in their face. Major message from Trump.
Arabs - 4 types exist in Israel, Israeli Arab, Palestinian Arabs under PA, Palestinian refugees, Hamas ruled Arabs -
They cannot accept Jewish rule on 'muslim conquered' lands. Against Islam. They are religious required to get it back.
Hatred of Jews and Christians embeded in Islam - Dhimmis
Thankfully most muslims are not so religious and don't follow