The thing is that if you put a tasty morsel in front of any wild animal it will sniff it, take a bite and then, should all its senses detect nothing other than deliciousness, eat it.
Now when such a morsel stands out from the crowd, for example, a bright green patch of spinach in the veggie patch that itself sits as an island in an ocean of nutrient-poor grey, then not only will the possum eat with delight the fresh watery greenness, it will see it from a mile away.
This is why humans have been forced to reduce the numbers of possums and any number of their cousins who might otherwise take advantage of us.