It's key empirical evidence. And yes one piece of evidence can invalidate an entire scenario, like the initial suspicions that (it was their 3rd 200ft dive) they ran out of O2 either on the ascent or shortly after surfacing and then the loop went hypoxic and he drowned. I along with may others suspected that in the days immediately after his death and that scenario is false. There was O2 in plenty sufficient quantities even after he lost consciousness and the loop was never hypoxic.Don't throw the baby out with the bathwater.
Overlooking or not reacting to one piece invalidates everything?
If you think he embolized and the embolism caused hypoxia in his brain that's all well and good, but there's no information to support or refute that. The time to body recovery along with the mess of the ME's office in Monroe County means that we are unlikely to ever get good information to assess your hypothesis.