Sloan was by far the longest tenured coach in the NBA and his 23 seasons with the Jazz are the most ever by an NBA coach with one team.
According to reports, Sloan has simply run out of gas and as he put it, "it's time to move on". His alleged confrontations and souring relationship with point guard Deron Williams also didn't help and made his decision that much easier to make.
Although Sloan never won an NBA Championship with the Jazz, he walks away as one of the most successful coaches in NBA history. He is third all-time in wins (1221) behind Don Nelson (1335) and Lenny Wilkens (1332). He is the only coach ever to win at least 1000 games with one team. Sloan won 1127 games with the Jazz (1988-2011) and 94 games in his only other coaching stint with the Chicago Bulls (1979-1982).
In 2009, Sloan was elected to the Basketball Hall of Fame as a coach.
As for his tenure, in the business of sports where coaches and managers have a short shelf life, Sloan was considered one of the "Last of the Mohicans". Now only Gregg Popovich of the San Antonio Spurs (1996-present) remains as the lone coach hired in the 20th century. Next on the longevity list is Doc Rivers of the Boston Celtics, who was hired relatively recently in 2004. So as we can see, Sloan (hired in 1988) was one of the last of an endangered species.
Anyway, as for Deron Williams, I don't know what his beef was with coach Sloan, but when someone hangs around long enough to coach a team for an NBA-record 23 seasons AND has a winning record in 22 of the 23 seasons AND is 1 of only 3 coaches in history with 15+ consecutive winning seasons AND has coached one of the most successful duos in NBA history (Hall of Famers Karl Malone and John Stockton) for almost their entire careers, I think they must have done something right and must have gotten along with a WHOLE LOT of people over the years. So I'm going to side with the old man on this one.
Lighten up Deron. You're great, but you're not that great.