For the bourgeoisie of the French Revolution, Marie Antoinette became that villain. In 1789, they still needed the King, so there was some reluctance to attack him as much, as they were forming a constitutional monarchy. However, when the royal family attempted to escape Paris, all bets were off.
It became common theory, that they were trying to escape to Austria, so Marie Antoinette would get help from her Habsburg family, and Austria would invade France. This conspiracy theory (not true, as it turns out) effectively lead[0] to two things; the establishment of a republic and pre-emptively invading neighbouring countries, like Austrian Netherlands (modern Belgium).
There is truth in every stereotype, and there are legitimate criticism of Marie Antoinette, but her character is far more complicated than her common cartoonish perception. This is how lines like 'let them eat cake' gets added afterwards, to justify the means.
[0] Yes, I know there were numerous other factors, but it's kind of astonishing how big of factor the Austrian conspiracy was.