Why? Killing them requires, well, doing something. You have to actually kill them, which takes effort, and then you have to dispose of the carcasses, which takes effort. On the other hand, simply turning them loose is no effort at all.

If you own a machete (or rampiri, or kukri), the marginal cost (and frankly effort) of killing a cobra is basically zero. And disposing of the dead ones has to be as easy or easier than disposing of live ones if you factor in any factors related to other people...

> a world where people dump hazardous waste into rivers to save money

That mostly comes down to insufficient education, greed and lack of immediate consequences.

Letting a live snake roam free is entirely different in that an uneducated man would understand the risk, there is no upside and there is a possibility for immediate consequence.

Because dehazarding waste is more difficult than chopping up a snake?

But letting the snakes go is even easier. Use the example of people littering instead of using a trash can, or not flushing public toilets, if you need a demonstration of how people can't be bothered with even simple tasks.

Most people aren't worried their litter will literally come back to bite them. Were the snake breeders really unconcerned that dumping a bunch of snakes out the back window wouldn't have consequences?

They were breeding poisonous snakes in a land where those snakes already live in the wild, I doubt they were worried about having a few more of those snakes out there.

These breeders were trying to scam a government program so they didn't exactly have the highest scruples, expecting them to do anything to aid society is probably too much to expect.

Besides the other explanation you got, the effect of any one breeder loosing his snakes was probably pretty small compared to the cumulative effect.

Happens in America, too.