The lizard-people conspiracy theory was popularized by conspiracy theorist David Icke
Contemporary belief in reptilians is mostly linked to British conspiracy theorist David Icke, who first published his book “The Biggest Secret” in 1998. Icke alleged that “the same interconnecting bloodlines have controlled the planet for thousands of years,” as the book’s Amazon description says. The book suggests that blood-drinking reptilians of extraterrestrial origin had been controlling the world for centuries, and even originated the Illuminati — a fictitious group of world leaders that conspiracy theorists say control the world.
Icke has long been accused of anti-Semitism, as his writings on the reptilian conspiracy theory are clearly evocative of the centuries-old blood-libel conspiracy theory, which alleged that a cabal of Jews were controlling the world and drinking the blood of Christian children. He has denied being anti-Semitic, The Guardian reported in 2001. Insider sent a message to Icke via the media-request contact form on his website, but had not heard back at press time.
re: lizardman constant, apparently:
found the above post by googling, also ran into this one on how to avoid the antisemetic trope, looking up both of which were inspired after seeing a comment on bsky (account required)