It’s a numbers game, and the slugs are winning.

Foxes eat rabbits all the time, but they literally breed like rabbits, so there’s a balance of sorts. Birds eat bugs all the time, but bugs lay millions of eggs to compensate. Same goes for bacteria too. Lots of little critters eat bacteria, but bacteria just multiply so fast that there’s always plenty to go around for everyone.

Most species are just brute forcing it with numbers instead of skill or planning. So far, it has worked well, and slugs are just repeating a billion year old exploit. Slow breeding animals like superb owls, elephants and humans are the exception.