He was fantastic in the CL run that year, especially on the QF return leg in Kiev
[video=dailymotion;xya01e]http://www.dailymotion.com/video/xya01e_1998-march-18-dinamo-kiev-ukraine-1-juventus-italy-4-champions-league_sport[/video]
up until 2010 international football was considered bigger than club football.
Whenever a major international tournament was on, whichever player played the best guaranteed they would win world's best player.
look at 2002 and 2006 for example. Ronaldo won player of the year despite being injured for most of the season for Inter and cannavaro won player of the year in 2006 despite not even getting past the quarters in the CL.
Things have changed now though club football is a lot bigger. Also the Balon dor and world player of the year merged into one, hence the emphasis on club football for these awards these days