Which is why it’s mocked and parodied (the Incredibles is another movie that mocks this trope a couple times), but I still wonder how many times, structurally, these monologues come from, say, a villains need to be Understood, or a drive to Prove his own intelligence over that of the hero, even if it’s more related to Plot Sequence than source of the problem.
But many times, the point of the Villain monologue is to tell the MC how they (the villain) were really behind all the events of the movie. Even if poorly done, this can show the MC and the audience the effect the Villain has had on the MC throughout and sometimes puts pressure on the MC to change (even if he/she does not change).
The point of bringing the question up, though, is I’m hoping to find ‘shortcuts’ to finding the source of a problem. It’s too easy to look at what characters are doing and say it comes from this or that quad only to realize later that what the characters are doing is not the problem but is in response to the problem. It just sort of hit me that often, in a monologue, you have a villain telling a hero that the whole time they’ve been doing one thing, another thing has been going on behind the scenes and the behind the scenes stuff is really what the hero is reacting to.