A successful film now reliably becomes a series, a game, a comic and a theme park attraction. The expansion follows from the fact that the costly asset is not the story but the audience's familiarity with it.
Familiarity is the expensive thing to build
Introducing a new world requires convincing an audience to invest attention in characters they have no reason to care about. That persuasion is what most marketing spending actually buys, and it fails often.
Once the audience knows a world, every subsequent product starts from a position no new property can buy at any price. The explanation is already done.
Expansion is therefore a way of amortizing a marketing investment that has already been made, rather than a separate creative decision taken on its own merits.
Different formats reach different audiences
A person who will not sit through a film may play a game set in the same world, and a reader may follow a comic that fills gaps between installments.
Each format has its own habitual audience, and a franchise present in several of them keeps encountering people the others never reach. The overlap is smaller than it appears.
That is why expansions are not simply retellings. A game version usually explores a period or character the films had no room for, so it has something of its own to offer.
Continuity between installments is the maintenance cost
Once several products claim to describe one world, they must be kept consistent, which requires a central group tracking what has been established and approving new material.
This is genuine ongoing labor and it constrains creators, since a game cannot casually kill a character the films intend to use later.
The alternative, letting each format contradict the others, works commercially but weakens the sense of a single world that made the expansion attractive.
Physical formats have the longest life
Theme park attractions and consumer products outlast the release cycle that produced them, continuing to earn from a property long after new installments have stopped.
They also serve as continuous advertising, keeping a world present in daily life for a generation of children who have not seen the original work.
That durability is why licensing decisions are made with a longer horizon than release schedules, and why some franchises persist commercially despite years without new stories.
Saturation is the real limit
Audiences tire of a world when supply outruns appetite, and the symptom is falling interest in each successive installment despite unchanged quality.
Rights holders manage this by spacing releases and varying tone, but the pressure to publish while a property is valuable pushes the other way.
Most franchise declines look like a collapse and are actually the accumulated result of releasing slightly too much for slightly too long.