Here's my theory: the story starts at the amusement park, with the goal of getting Guybrush to run away from Chuckie again. In this phase we control both Guybrush as a child and Elaine wich still is in the "world of Monkey Island". At that moment someone (Largo ?) Sees Elaine and discovers the true power of Big Whoop.
This prologue ends with the beginning of Curse, with Guybrush in the autoscript car lost in the ocean.
There is a time jump of many years, and now we are in the real world. Guybrush, now 50 years old (here is that insistence of the biographical element to which Dave always mentions ...) is recalled by Murray to "return to Monkey Island": in fact, during his absence a form of cruel dictatorship has been established that uses the powerful black magic of the seals (Goetia) and that has imprisoned Lechuk, taking over his crew of ghosts. This interpretation is deducible from the strange seals that appear in several images (the ghost that loads the ship, the courthouse, the streets of Melee) attributable to this species of new culture or power that has settled in the Caribbean and that gives great importance to the keys, as seen in the blacksmith screen and the painting in the courtroom. Maybe they are the keys to accessing the true power of Big Whoop, which has to do with time?
Anyway this 50-year-old Guybrush returns to Melee, having forgotten most of his past as a pirate, and must therefore first try to remember who he was and then try to end the power of this new dictatorship, with the help of Elaine and Lechuck himself.
I imagine there may be numerous "time travel" or paradoxes, similar to that old design document posted by Ron in 2020, "Time Fly".