Assessments of a film or series often change substantially on a second viewing, and the changes go in both directions. The reason is that the second encounter measures different properties from the first.
Surprise can only be measured once
A first viewing is partly an experience of not knowing what happens next, and that uncertainty contributes heavily to how tense, funny or affecting something feels.
On a second viewing the uncertainty is gone, and whatever remains has to work without it, which is a genuinely harder test that some works pass and others do not.
Works built primarily on a reveal tend to lose the most, since the machinery that produced the effect is visible and the effect itself cannot be repeated.
Attention moves to construction
A viewer who knows the plot stops tracking it and starts noticing how scenes are built, what is being set up and how performances are calibrated against information the character lacks.
Details that were invisible under the pressure of following a story become legible, and careful work that went unnoticed the first time becomes the main source of pleasure.
Pacing is experienced differently
Sequences that felt slow often improve, because the impatience of wanting to know what happens has been removed and the scene can be watched for what it contains.
The opposite also occurs, where a stretch that seemed purposeful is revealed as filler once the viewer knows nothing in it matters to the outcome.
This is why opinions about a work's length so often shift on revisiting, in either direction, without anything about the work having changed.
Expectation no longer distorts the response
A first viewing is measured against whatever the marketing, the reputation or the genre promised, and disappointment at not receiving that can obscure what was actually delivered.
The second time, the work is assessed as the thing it is, which is why films that frustrated audiences on release are frequently reconsidered later.
Why critics rarely get the chance
Review schedules are built around a single screening close to publication, so most published criticism records a first impression under time pressure.
Reassessments written years later are common precisely because the second viewing produces a different and often more durable judgment.
The gap between those two kinds of writing is a difference in what was measured rather than a sign that anyone was wrong.