How did sophistry come to mean reasoning that seems convincing but is unsound?

The term sophist originally derived from the Greek sophistēs, meaning "wise man" or "expert," and was initially applied to sages, poets, and early philosophers. However, the transition of "sophistry" to mean unsound or deceptive reasoning is primarily the result of the critical influence of Plato and Aristotle.12

These philosophers characterized the professional teachers of the 5th century BCE as individuals who prioritized victory in debate over the pursuit of truth. Plato, in particular, frequently accused them of using "eristic"—arguments aimed solely at winning—and "antilogic," a method of assigning a counterargument to any position to negate it. By framing these techniques as dishonest or "sham" philosophy, Plato and Aristotle successfully altered the term's meaning. Consequently, sophist evolved from a title of wisdom to a label for a "captious or fallacious reasoner," and sophistry came to describe reasoning that appears plausible on a superficial level but is actually unsound or intended to deceive.3214