In my country a white christian radical murdered 6 Muslims after the immigration ban was announced.
It is not a ban on all muslims or all muslim based countries. You’re right. After all a number of Muslim countries, including the one that produced most of the 9/11 terrorists, weren’t included in the ban. But that doesn’t mean it’s not based on religion. There isn’t really any reasonable explanation of what it is meant to do since there is ALREADY extreme vetting of immigrants.
There’s a lot of great information about the order here: https://www.washingtonpost.com/graphics/national/immigration-order-explainer/