Australia happens to have a lot of reptilain predators, not just snakes and most of the snakes aren’t highly toxic. A variable climate and low productivity favours reptiles over mammals. Competition and sheer number of species ensures a good number of nasties. However that has little to do with a scarcity of prey. The inland taipan is a dry country species, and happens to be the most toxic of the land snakes. However other taipan species are only marginally less toxic and are animals of the coastal belt or even the wet tropics. The most common Taipan species extends well into the rainforests of northern Australia and PNG. These areas support huge rodent and reptie populations. Similary the death adder, Australia’s other highly toxic snake is a creature of the wet coastal forests as much as the dry inland. The same pattern is seen worldwide. Desert snakes on average don’t have any more potent venom than snakes of the wetter areas.
I agree with you snakes have potent venom because of a need for speed and certainty, which is exactly what I said above.
