Okay, so I AM NOT A SCIENCIST but I do play a science editor at work, so here's a few things I've managed to put together with some internet research. Someone please check me if I've got this wrong.

First, this antibody treatment isn't something they whipped up in the WH tub.

The head of Renergon, who provided the treatment is (I have read) a buddy of Trump's. This is a treatment that has been discussed and in development for several months now, but it was only just entering serious trials in September. https://www.sciencemag.org/news/2020/09/provocative-results-boost-hopes-antibody-treatment-covid-19

Interestingly, they were planning on trialing the drug on high risk groups (older people, overweight people [their words not mine], and diabetics). So Trump is actually an ideal guinea pig.

Based on the article linked above, they found the treatment worked best in people who/

had no previous antibodies to COVID19; if that were the case, there was a good chance of having a lighter viral load (less virus there to make you sick). But they had only trialed it on a couple hundred people and were looking to move it along quickly.

So Trump gets the treatment 'cause he's got a buddy, clearly, but also, to be super clear? He got the treatment because he's wealthy (even if he's in debt up to his bad toupee). Insurance doesn't pay for experimental treatments, as a general rule; you get enrolled in trials.

ANYWAY that's why the language on that one headline that's floating around; there's a "race" to see whether his body can produce antibodies faster than the virus can reproduce. Which is basically the case any time someone gets a virus, but someone made a clickbait headline.