Sequels to large films are frequently announced or quietly commissioned before the first film has been seen by an audience. The reasoning is scheduling rather than confidence.
Large productions need years of lead time
A film built around visual effects, location work and a heavy stunt programme takes years from script to delivery, and the effects work alone occupies much of the back end.
Waiting for opening-weekend results before starting that clock pushes a sequel several years further out, into a period when the audience's attention has moved.
Committing early is a way of buying back that time, and the commitment usually starts as development work rather than a full production order.
People become unavailable quickly
Leading actors book years ahead, and so do the department heads who define how a film looks and sounds.
Once a crew disperses, reassembling the same group is difficult and expensive. Each person has taken another job with its own dates.
Options are therefore written into the original contracts, fixing terms and reserving windows before anyone knows whether the first film worked.
Sets and assets are cheaper to keep than to rebuild
Physical sets, digital models, costumes and rigs represent a large sunk investment that degrades once storage becomes the only reason to keep it.
Rebuilding a digital environment or a practical set from scratch costs close to what it cost the first time, and often more.
Continuing straight into a follow-up spreads that cost across two films, which changes the arithmetic on both.
Release calendars are claimed years ahead
Studios reserve dates far in advance, because the strongest weekends are contested and a title that moves late usually lands somewhere worse.
Holding a date requires something to put in it, so slates are assembled from projects that have been committed to rather than proven.
A sequel is the easiest thing to place there, because its audience is already identified and its marketing does not have to start from nothing.
The risk is a finished film with nowhere to go
The obvious hazard is a first film that underperforms while its successor is already shooting.
Studios manage this by staging the commitment: writing continues, casting holds, but the expensive phase waits for early signals such as presales and international interest.
When those signals are misread, the result is a completed sequel that sits unreleased or is quietly reworked, which is a visible reminder that the early commitment is a bet rather than a plan.