I have found at least twice the adjective “infamous” used, apparently, to mean “very famous”, rather than its actual, opposite meaning, both times in non-humorous texts:
The first, a historical essay about ancient Spartan lawgiver Lycurgus:
At some point between the late eighth and mid-seventh century BC ... a new constitution came into force in Sparta; known as the Great Rhetra, this constitution was, by the fifth century BC, associated directly with Sparta's infamous lawgiver Lycurgus...
And the second, a popular science article about the Goodyear blimp:
3 June 1925: The infamous Goodyear blimp first flies. These would go on to be a regular part of sporting events in the US.
Is this a new use of the term? Or were those most likely plain oversights?
If it matters, both texts are by British authors.