It wasn't a matter of wins and losses, as the Warriors have enjoyed their greatest success in decades under Jackson.
Apparently he didn't mesh well with the front office, so they decided to go in a different direction.
The Warriors went 23-43 in Jackson's first season, which was shortened by the NBA lockout. The next year, they went 47-35 and lost in the 2nd round of the playoffs. This year, they won 51 games, only to lose to the Clippers in a tough 7-game first round battle.
Warriors owner Joe Lacob explained the reasoning behind Jackson's dismissal:
We'll see if the Warriors manage to find the right person for the job.