I'm not in Syria and thus can only repeat what other people say, but I've heard that ISIS is committing genocide against Christians, Yazidis, and Shiites. The source of this information is John Kerry.
Again: Trump campaigned very specifically on a ban on Muslims. The religious minority directive is obviously an attempt to scope the restriction to adherents of Islam. It is worded in the way it is, again obviously, to make it more likely to withstand the pending legal challenges.
This isn't a tortured or biased interpretation of the directive. It is precisely the description Trump used over and over and over again on the campaign trail.
> Of course, one plausible explanation is that Democrats don't like Christians
That's a conspiracy theory with no evidence, not a plausible explanation. Refugees can't vote for a long time. There are too few to make any substantive electoral difference.
From another comment thread: "Refugees are referred to the US by the UNHCR.". You're also comparing the percentage to the total population of the country, rather than those who applied for asylum/refugee status. This is not a meaningful comparison. Finally, you provide no year-over-year data; it's possible that they fled first in previous years, or are residing in areas that are protected by pro-Assad forces.