It seems that given effectiveness of UV treatment on surfaces, he extrapolated its potential to use within the body. Just because he landed on a solution that on paper sounds like an anti-bacterial cure from the 40s and 50s doesn't mean that is the same treatment he was suggesting.

I think rsynnott is saying it's pure coincidence that what he suggested sounds like UBI and it's likely that UBI is a term Trump has never heard before.