Win shares are bases on team wins, every team win creates 3 win shares to be divided amongst the teams players.
The 1908 Pirates won 98 games, creating a substantial amount of win shars. Looking at
team stats , it becomes clear that Honus was by far and away the driving force on that team. He hit 90 points higher than the next regular, and slugged 160 points higher.
The 1908 Pirates had the best season ever for a one man team and thus that man got the highest winshares season ever.