Death by hypoxia can be caused by airway obstruction(strangulation) or poison(cyanide, CO).
In the case, there is a toxicology report saying the victim is poisoned by cyanide. The organ damaged also diffuse and not concentrated. Cyanide works by inhibiting an enzyme in the mitochondria that use oxygen. Therefore, the cells can't oxygen for cellular respiration, cause the tissue die of hypoxia. The oxygen is there but it can't be used. The laboratory report that found high oxygen level in the blood also supports the cyanide poisoning.
