I read a while ago that Rivaldo was displeased with the position he was played at under Van Gaal. Limited his abilities, he said. Not a team player, as you said and likely the reason Van Gaal wanted him out of the club.
Rivaldo at that time still played mostly as a LW. Van Gaal wanted him to play there and there was no problem in his first two season. But in 1999/2000 season, Rivaldo asked to play in a 10 role like with Brazil team. Van Gaal refused and benched him for a few matches. After that their relationship was completely destroyed.
Despite of his creativity and passing skill, Rivaldo could be really selfish with his plays. Even Platini once said the last time Rivaldo passed was when he played on street.
But whatever his problem, he became an eternal icon for Barca after the historic hattrick. And same thing for Brazil after 2002 World Cup.