I came across a description of Enigmarelle in Will Self's excellent novel Umbrella. In the novel, a crowd is gathered to witness the marvel that is Enigmarelle. One character is, along with the rest of the crowd, buying it, entranced, while the other character is shocked at how obvious the ruse is. But she's alone in that opinion, and that seems like an accurate portrayal of Enigmarelle's reception--the Wikipedia article linked mentions an article in Scientific American that (judged by its title; it's sadly behind a paywall) appears to enthuse over this "clever mechanical and electrical automaton." Was everyone so duped? How?
Looking a picture of Enigmarelle, it's obvious to my modern eye how fake it is. Of course, I know what robots are capable of looking like and accomplishing, while contemporary viewers had a much harder go of it. Nevertheless, was everyone really so duped? Was there any skepticism, if not from the masses than from other experts? How do we now know Enigmarelle was fake (besides using our modern eyes)?
Is the whole book in print/ebook really like this? Wow, that's exhausting to read.
I think you've misunderstood the passage here. The wonder that audiences are flocking to see is what they believe to be an automaton and is being marketed as such. Credulous Stan says "ortomaton" in his accented English, and "'e's drivin' it!" in reference to the showman turning the crank to make it go.
The fakery that Audrey detects isn't an automaton masquerading as human. It's a human-powered puppet masquerading as an automaton:
Besides [thinks Audrey...I think], who could be fooled by that metal visor, below which an irresolute chin is plastered with thick stage paint
In other words, there's a person in there making the "automaton" go through its repetitive, not-actually-automatic movements.
The editor's note in the Scientific American article describing the automaton and how it was said to operate mechanically to this effect:
(The photographs of this automaton were submitted to the managers of a well-known New York theatrical enterprise, and they at once stated that they had seen the automaton in London and that there was really a man concealed in the midst of this aggregation of machinery.)
The more notorious controversy over whether something was a genuine automaton concerned an earlier exhibit called The Chess Player--or, in a phrase you might know today for a different reason, The Mechanical Turk. The Chess Player actually played chess. That is, the people operating it were chess masters themselves, and intelligently played against (generally defeating) their opponents.
Edgar Allen Poe's "Maelzel's Chess Player" is the classic takedown of the Player being a genuine automaton--but his need to write points to genuine credulity among at least some people over the entirely mechanical innards of the creation.