The World Cup has grown, and the tournament arriving in North America is larger than any before it. A bigger field changes what winning the scoring award requires.
More group matches means more scoring against weaker sides
Expansion admits teams that would previously not have qualified, which widens the gap in quality between the strongest and weakest participants.
Forwards from leading nations therefore face at least some opposition that concedes chances at a rate the old format produced less often.
Goals accumulated in those matches count identically to goals in a semifinal, which shifts the award toward players with favorable early draws.
The path to the final is longer
A larger bracket means more knockout rounds, so a forward whose team goes deep has additional matches in which to score.
That strengthens the existing bias toward players from the most successful teams, since reaching the final has always been the main route to the prize.
A striker eliminated early now sits further behind, because the finalists have more remaining opportunities than in previous formats.
Knockout soccer still suppresses goals
Elimination matches are cautious, and scoring rates in them fall well below group stage levels regardless of how many teams are involved.
So the extra rounds provide opportunity without providing easy goals, and forwards often find the additional matches yield less than the arithmetic suggests.
The award is consequently decided more often in the group stage than the structure of the tournament would imply.
Squad rotation dilutes individual totals
A longer tournament in summer heat forces coaches to rest players, and forwards are among the first rotated when a group is already won.
Minutes lost that way are minutes in which a striker cannot score, and a player whose team qualifies early can be rested into a lower total.
Which produces the odd result that a comfortable qualification can cost a forward the award his team's strength helped him contend for.
Tie-breaks become more likely as fields grow
More teams and more matches produce more players clustered near the top, and shared totals at the end of a tournament are a recurring outcome.
Assists are commonly used to separate them, followed by minutes played, which rewards the forward who did more with less time on the field.
That rule quietly favors substitutes and rotated players, and it is the part of the award most likely to decide the outcome in an expanded format.