Awards that compare scorers across different countries cannot simply add up goals. The weighting applied to each league is where the real decision is made, and it changes winners routinely.
Raw totals reward the weakest competition
Scoring is easier in leagues where defensive organisation is less developed, so an unweighted award would consistently be won outside the strongest divisions.
That outcome was widely seen as unsatisfactory, since the award was intended to identify the outstanding goalscorer rather than the most favourable environment.
The weighting exists to correct for that, which means the award has always been an adjusted measure rather than a count.
The weightings come from competition performance
League factors are typically derived from how clubs in each country perform in continental competition over a period of several seasons.
The reasoning is that results between clubs from different countries are the only direct evidence about relative strength available.
Because those results accumulate slowly, the weightings lag reality, and a league improving rapidly is undervalued for years.
Small differences produce large effects
Multiplying a season's goals by a factor magnifies the gap between leagues, so a modest difference in weighting can overturn a substantial difference in goals.
A forward scoring heavily in a league one tier down in the weighting must outscore his rival considerably to finish ahead.
Readers see the final ordering without the multipliers, which makes the results look arbitrary when they are simply the arithmetic working as designed.
The cut-off between tiers is contentious
Leagues sitting just above or below a threshold receive noticeably different treatment despite being close in strength.
A forward's chances therefore depend partly on which side of a line his competition fell on when the factors were last set.
Every proposed alternative faces the same problem, because any continuous measure has to be converted into something usable at some point.
What the weighting cannot capture
League strength varies internally, and a scorer at a dominant club faces weaker opposition within his own competition than a rival at a mid-table one.
No weighting adjusts for that, so the correction operates between countries while ignoring an equally large difference inside them.
The award is best read as a rough comparison rather than a settled answer, which is roughly how the people who calculate it describe it themselves.