In short, because people very much like to drop a nuke on something when a firecracker would do the job.
The tools and amulets most associated with what we would consider “not the nicest sort of magic” to downright “roofie spells” are often obtained via the torture and slow death of an animal. That’s no coincidence. Toads are powerful creatures and the unscrupulous will manipulate, twist, and torture that power to their own ends.
Toads are born in and breathe water, then shape-shift and learn to walk on land and breathe air. They traverse the under and overworlds with ease. They are wild, warty, and yet can be hand-tamed even in their wild state. Full wild toads will take crickets from your fingertips if you’re careful and quiet. They sing and “speak”, and can even answer the occasional question (if you’re willing to accept peeps and croaks as an answer).
So, I do not think the toad specifically embodies the power to manipulate. I think it has power, and people use it for that end.
Toads are historically associated with rewarding kind people with the secrets of immortality and the like. I shudder to think of what they do to people who crucify them on anthills.
Perfect response to things I’ve seen going around in the past is perfect.
We had/have a toad living under the porch. I had to relocate him when the dog found his hiding place. I’ve been curious about toad lore that didn’t involve hurting the cute little bugger.
I mean, you have the “Frog Prince” type stories which are well and good. I believe the stories I remember about kind treatment, wortcunning, and immortality was from Japan.
My personal experience has been that the kinder you are to a frog, toad, or aligned spirit the kinder they will be toward you. I also tend to notice their numbers swelling locally after intensive work with the “great toad”.
However? Just being kind to animals in general is always an excellent thing. I don’t even know if it is specific, but… shit tends to go better in my life when I take the time to be kind and helpful to critters.
In Cornish Pellar craft as Gemma Gary describes it you utilize found dried or dead toads rather than torturing them to death. I have such a little guy—he probably just died a natural death on the road. I think generally its a better way to go, most folks have never killed a vertibrate in their life and there is no reason to start with a toad. (If you want to take up animal slaughter why not start with a food animal like chicken? and learn to do it with a minimal of pain—quick and merciful as is honorable to the animal as a food source).