Queen Anne knighted Isaac Newton during a royal visit to Cambridge, a gesture widely understood as political: Newton was standing for Parliament and the honor bolstered his campaign. By then Newton was Master of the Royal Mint and president of the Royal Society, decades removed from the Principia, and the knighthood cemented his status as England's most celebrated natural philosopher.
By 1705 Isaac Newton had already transformed physics and mathematics with the Principia Mathematica two decades earlier, but he had also reinvented himself as a public official, running the Royal Mint with the same obsessive rigor he'd once applied to celestial mechanics, personally interrogating counterfeiters and sending several to the gallows.
Queen Anne's visit to Cambridge in the spring of 1705 coincided with Newton's parliamentary ambitions; he was campaigning, unsuccessfully as it turned out, to represent the university in Parliament. The knighthood, conferred at Trinity College, was less a recognition of scientific achievement than a piece of electoral theater, though it stuck regardless of the election's outcome.
Newton would go on to feud bitterly with Leibniz over calculus and with Flamsteed over astronomical data, ruling the Royal Society as an increasingly autocratic president until his death in 1727. The knighthood gave him the title history remembers him by, even though, by his own scientific standards, it was among the least consequential moments of his career.