eli5: Why do snakes have such potent venom when the prey they eat are normally small in comparison?

Question

I’m from northern Australia and we have many snakes that can easily kill humans, cattle and other live stock. The power of these snakes venom seems overkill for what is required?

In: 139

Answer 1

Evolution doesn’t work like “we evolve the minimum nescessary” it works like this: “the most efficient at survival produces most offspring, spreading his genes” as long as there is no downside to stronger venom its more efficient and therefore has a higher chance to become a dominant feature in a species.
And there is no downside. Producing a more potent venom does not cost a snake significantly more energy or something while killing prey faster conserves energy.