You seemed to have missed that most “Trump supporters” that post in those groups (less so for the ones that comment), especially those that capitalize each word or that ask for Amens, are trolls: Russian, Macedonian, sometimes Philippino or from some other authoritarian or ex-URSS country. Go look at their profile and you’ll notice that they’re strange (because they’re fake). You’ll also notice the exact same thing posted by two seperate people, because they’re just two accounts that are administered by the same person. Sometimes they don’t even bother to hide the fact that they’re clearly not American, and as soon as you go in their profile you’ll see that they’re from Skopje or Moscow. You can also reverse-image search their profile picture and find where they picked them up. Sexy woman? Usually from a porn site.
Fact is, Facebook is a digital warfare playground. What you’re seeing in there is not organic discussion but an organized disinformation campaign by an authoritarian coalition led by Russia, constructed to polarize and extremize the « trumpists » to support the authoritarianization of the States. The aim is the destruction of liberal democracy, especially (but not exclusively) in the US, and this computational populist propaganda is their primary weapon.