In 2002/03 season when Henry got 20 assists, Manchester United won the league:
Scholes who was playing double pivot in the midfield had 14 goals and 3 assists in 31 league games.
Giggs had 8 goals and 10 assists in 32 games in the league
Van Nistlerooy had 25 goals and 4 assists in the league
All these United players performed exceptionally well and topped it up by winning the league yet Henry was the one who won PFA player of the year.
It's not about winning the league, it's about who has been the best individually.