weah's ballon d'or was a combination of 2 things:
1)no clear favourite for the award
that year, there was no world cup, and no euro champs, no african cup of nations either
-in italy: ac milan reached the final of the champions league with an excellent paolo maldini, but they lost it and finished only 4th of the italian league
batistuta was the top scorer of the league but unfortunately his team (fiorentina) didn't have good enough results
-in germany: dortmund (with sammer) reached the semi final of the champions league, but they finished obly 6th of the german league
-in spain: real madrid won the league with zamorano being the top scorer and laudrup the best player, but they did nothing in champions league
-in premiere league: the big names weren't successful, and blackburn surprisingly won the league, with an incredible alan shearer (34 goals)
-ajax won the champions league, but it was with a very young team, and they don't give the ballon d'or to young players
litmanen was only 23 years old for example
2)the context
the amount of foreign players in europe was increasing, and there was a lot of talk about allowing more foreign players in european clubs
the very famous bosman ruling (which allowed the european clubs to have as many foreign players as they wanted) was adopted that year, just before they gave the award to weah...
as a consequence, the rule changed for the ballon d'or award that year, for the first time the award was for the best payer - of any nationality - in europe, while before it was for the best european player
it was obvious that they were going to give the award to a non-european player (because romario didn't won it for being brazilian, while he dominated european football the year before)
the best non-europeans were the chilean zamorano with real madrid, and the argentine batistuta for fiorentina
but they were not africans
let's have a look at weah's season that year:
weah played in the french league, for PSG
that year, he had the worst season in his career
he scored only 7 goals in the french league, his team mates ginola and rai scored much more than him and they were middlefielders, he scored 1 goal every 384 minutes, which is very very bad
he scored 7 goals in champions league, but 5 out of these 7 goals were scored in the group stages, 4 against spartak moscow and dynamo kiev
he didn't score in the second leg of the quarter finals, and he didn't score in the semi finals either
the ballon d'or is awarded at the half of the season, so we must also take into account his start of the season with his new club, ac milan: 6 goals in 14 matches in serie A, and 3 goals in 5 matches in champions league, agaisnt a bad polish club and a czech club
overall, his stats for this year (taking into account the start of the season with ac milan) are 1 goal every 275 minutes, which is pretty bad
he didn't win any major title either, since PSG didn't won the champions league, and nantes won the french league
so it's fair to say that, as expected, weah's ballon d'or was the least deserved in history, he only won it because he was african and so he became the first african to ever win the award (and the only one so far)