I'm sorry but this is just lazy writing. You can't just reveal a villain just to advance the plot.
Also the way you reveal it:
"Oh whoops, I made a mistake and said something I shouldn't have. Guess I have no choice. Time to act up."
This is not how you reveal a calculating villain. You introduce the character as a sly fox, planned and charismatic; using these traits to lure his victims. And then he makes a mistake like a dumbass and reveals everything ?
Even if the character was already suspicious of him, this is stupid.