You obviously didn't watch the news conference. The context was, the director of a DHS live environment decontamination lab was talking about how to decontaminate surfaces and areas that had novel corona virus on them. The lab director talked about how well/quickly various cleaning products or environmental conditions killed the virus on different, common surfaces. He never discussed therapies of any sort because he doesn't treat humans, he treats surfaces (and IIRC he's an organic chemist, not a medical doctor).
The lab director head just finished talking about how bleach products (specifically Lysol) and UV light killed the virus. It was at that point, President Dumb **** asked if you could inject the disinfectant into the body (he never said bleach but as the lab director just had and that's to whom Trump was responding had it was clear that's what he was talking about). He also asked about light being brought into the body.
The briefing was never about "light therapy" because the expert briefing didn't treat humans, just surfaces.