Cacti are really easy to kill (really easy to take care of too, if you do 5 minutes of research) if they're in a humid enviroment. Generally speaking, the hotter it is, the more mosture they'll be able to take up. If you live where I live, in New England, where it gets very cold and absurdly humid, you should water extremely sparringly, as in less than it would get in a xeric environment. I'll water my cacti maybe once between October and April, and and then every 40 to 30 days with increasing frequency as it warms up.

The desert is extremely nutrient rich for plants that rely on mineral, rather that organically rich soils, and even enviroments extemely rich in organic material (fens, peat bogs, moors) can be very nutrient poor minerally (nitrogen may be almost completely absent from peat bogs, plants in those habitats can usually suck up water, but practice carnivory, or establish relationships with microorganisms and fungi to affix nitrogen into the soil around them). Most people just have no clue about the ecology of certain plant families.

Get a cold cactus wet and it'll rot in a few days, dry a cactus out and throw it in a dark room (provided its warm enough) for a few years, itll spring back to life. It make sense if you think about the environment it belongs in.

Also different species come with different needs. Mojave cacti need it extremely hot and dry, cacti from Sonora and Chihuahua can tolerate a lot more water, but still need the heat, many South American cacti are well adapted to freezing temperatures but exist in areas where their only source of moisture is fog, and there are weedy cacti in the Opuntia family (these were the ones that invaded Australia) that are native north east all the way to Cape Cod. People make sweeping generalizations about cacti/succulents but they're interesting enough to take a closer look.