So everyone knows about the Salem witch trials and everything and while I am very interested in history, but I never learned much about the witch trials besides basic things. Anyways, my question, assuming the whole “if we drop her in the water and she sinks or we hold her under the water and she drowns then she’s innocent and if she survives then she’s a witch” thing is true, then why didn’t they just realize like “hey, these women with rocks tied to them and who are lowered in and held there by being tied to a wooden pole basically are literally ALL dying”? Like surely there’d be people who’d think hey if we’ve done this to all these women and not a single one has been guilty, why don’t we stop sooner?
Start by thinking about what how you might believe things that other people now or in the future might find strange to accept as a truth. If you're Catholic, you probably believe the Eucharist is the body of Christ. If you're superstitious, you might believe walking under a ladder is bad luck. You might even believe in the Flying Spaghetti Monster. Whatever you believe, in 1, 2, or 3 centuries from now, people might classify your beliefs as stupid regardless of how legitimate or serious your beliefs are to you at this moment. Now, you could argue about the veracity of beliefs. You can argue that some religious beliefs are fronts to portray morality when bigotry is more accurate. Slaveowners certainly hid behind Christianity to justify chattel slavery. Psychics may claim supernatural powers for fiscal gain. In short, approaching belief from a historical perspective requires a lot of careful interrogation as to why someone might pretend to believe something, might more easily accept a code, or truly believe an ideology. This takes us to Salem in 1692.
First, the water test you're referring to was never used in Salem. Rev. Increase Mather of Boston opposed it, therefore Massachusetts Bay did not practice it. The test was used throughout Europe. One way to address why people continued to believe in the water is that they believed, and they believed it because stories about successful cases spread. The mythology behind this test allowed people to believe it.
Second, this question is really more about why people believe in witches. This is one focus of my research on Salem. The year 1692 was full of division in Salem (a town composed of Salem Town and Salem Village). Two political factions vied for power to either make Salem Village independent or keep it as a community under the control of Salem Town. This was the culmination of decades of conflict. Just ten years earlier, Jeremiah Watts wrote described the Village as "brother against brother, neighbor against neighbor." People, even within families hated each other. Magistrate John Hathorne visited the Village in 1687, five years before he signed warrants for witchcraft. He described the situation as riddled with "uncharitable expressions" and "prejudice" that would "let out peace and order". Salem was also dangerously close to the frontier that saw continuous violence from Indian attacks over the decades. Most people believed any day could have been the next major battle, and Salem could be the location. A native driven perspective of this period is fascinating since it places the witch trials in a vastly different context. The constant threat of attack only intensified the internal strugglies within Salem. All this hatred, anger, distrust, and fear exploded in the witchcraft accusations.
When the accusations began, they targeted easy suspects, and slowly targeted more people higher up the social ladder. By "coincidence" the accusations started with one faction of the independence conflict and family members of the opposition were targeted. So consider this- people you hate are accused of witchcraft. What motivation do you have to speak up? If you speak out, you're more likely to be accused, so its better to stay quiet or join the accusations than save your political enemies. The accusations fall within the dominant religious tradition of New England, so the core tenants of witch hunting already make sense. If anything, you would expect a witch to be someone you didn't like in real life, especially if you were a good Puritan watching for signs of Satan's minions.
If anything, the Salem witch hunters weren't stupid. They were calculating opportunists enacting an agenda on their own ideologies and prejudices. Convenient beliefs allowed witch hunters to murder their neighbors. We can't think of them as bumbling idiots who stumbled into killing sprees. They understood how their religion justified cruelty; it let themselves believe the righteousness of their own actions. And if we stop seeing the witch hunters as intelligent, we might miss the ones working to instigate the next Salem.