What was the public's relationship with sharks prior to this? Were they a well known predator to the public prior to this?

The answer to these questions is a bit complicated. On one hand, as I went into an an answer of mine a few days ago a good many Westerners appreciated the danger of sharks and shark attacks during the eighteenth and early nineteenth centuries. However, shark attacks largely became associated with maritime disasters and this association continued in he Victorian and Edwardian Eras. Winslow Homer's justly famous 1899 painting The Gulf Stream depicted an environment where most Westerners associated shark attacks: the deep ocean. This helped cement an image of the shark as an opportunistic feeder. Melville's poem "The Maldive Shark" acknowledged the animal's raw power, but claimed the pilot fish was the true brains of the operation:

They are friends; and friendly they guide him to prey,/ Yet never partake of the treat— /Eyes and brains to the dotard lethargic and dull,/ Pale ravener of horrible meat.

Similarly, several passages in Moby Dick liken the shark to ravenous dogs. While Melville's invocation of the shark was laden with symbolism like a lot of his work (although Ron Swanson vehemently disagrees ), he did borrow heavily from contemporary zoological studies of the animal. William Somerville Orr's 1855 entry on the pilot fish in Orr's Circle of the Sciences quoted several observers that the smaller fish frequently acted as a guide for its larger brethren. The Smithsonian's ichthyologist George Brown Goode wrote that 1887 book American Fishes that although many of the stories about the pilot fish's guiding the sharks were apocryphal, they had some element of truth to them.

The notion that the shark was a scavenger, albeit a dangerous one, became quite common by the late nineteenth century. Writing in the magazine The Californian in December 1893, the angler J Herndon Campbell regaled his readers with tales of the great white shark's ferocity when hooked and even once carrying off a fisherman, but he concluded:

such attacks are exceptional, the shark being as a rule, a cowardly scavenger; not ornamental, but a valuable animal filling the place in the ocean that the vulture does on land.

Other accounts from the nineteenth century likened sharks to hyenas and jackals. In a widely quoted sketch of the sharks' biology in the 1870s intended for children, the pedagogue Lady Verney contended:

The shark is the scavenger of the sea, the equivalent of the hyena on land, and he swallows whole whatever offal is flung overboard from the ships- bolting it without any action of the teeth, unless when his prey is too large to go conveiently down his throat, and he breaks it up as it passes.

The shark's image of a ferocious and cowardly scavenger had been set by the turn of the century.

This conventional wisdom about shark behavior made it much harder to comprehend the instances where sharks did attack bathers. The Matawan attacks forced the mainstream American scientific establishment to reevaluate its estimations of the capabilities of sharks. A good many scientists had dismissed tales of a shark's power as fishing tales. While they did not think they were harmless, they did not believe them to be capable of consuming a live human. The Brooklyn Museum's Science Bulletin issued a report on Atlantic sharks a few months before the Matawan attacks and concluded that sharks were not a danger to bathers. Both Treadwell Nichols, the curator of the Department of Fishes at the American Museum of natural history and Robin Cushwood Murphy at the Brooklyn Museum asserted that most shark victims had already drowned and thus offered no resistance. Frederick A Lucas, the director of the American Museum of Natural History, asserted in a letter to the Science Bulletin that:

One of the commonest statements is that "the shark bit off the man's leg as though it were a carrot," an assertion that shows the maker or writer of it had little idea of the strength of the apparatus needed to perform such an amputation. Certainly no shark recorded as having been taken in these waters could possibly perform such an act, though this might occur if a shark thirty feet or more in length happened to catch a man fairly on the knee joint where no severing of the bone were necessary. The next time one carves a leg of lamb, let him speculate on the power required to sever this at one stroke- and the bones of a sheep are much lighter than those of a man. Moreover, a shark, popular belief to the contrary notwithstanding, in not particularly strong in the jaws.

Although it's tempting to accuse these men of hubris, there were great difficulties in researching and collecting data on sharks during this time period. The 1917 issue of Copeia, the journal for American Society of Ichthyologists and Herpetologists lamented that "we cannot transport a shark 10 to 50 feet in length, and weighing from 300 to 10,000 pounds or more, with ease to our laboratories, and very often our field notes do not suffice for identification purposes." Copeia noted that most studies of sharks came from dead specimens. These naturalists often operated in the dark about sharks; notice how the above notes take it as a given that sharks could reach above 30 feet. This was because a set of Great White jaws from Port Fairy, Australia had allegedly came from a 36.5 foot specimen, which was not debunked until 1972.

But Matawan attacks did lead to a change in the perception of sharks both among the public and within the scientific community (although the former was arguably more swayed by Jaws, which Benchley admitted was itself influenced by Matawan). The number and close proximity of the attacks undercut claims that shark attacks on bathers were isolated examples, and a number ichthyologists put the blame on the attacks on a rogue shark. This theory, which originated in the tigers of India, posited that some animals developed a taste for human flesh and learned how to prey on humans when they were most vulnerable. Although the rogue theory is discredited (but it had a long lifespan, Hooper in the film Jaws mentions the shark is a rogue before he and Brody go out to find Ben Gardiner's boat), it does signify an acceptance of the shark as a different kind of predator than a hyena or vulture. While humans have understood that sharks were dangerous, Pliny the Elder has an account of a shark attack, the twentieth century saw a cognitive shift of the shark into a predator that actively actively hunted man as opposed to one that fed on humans when the opportunity presented itself.