I don't think Corbin did a "good job." I think he did about as good as 80-90% of coaches would have done under the circumstances. He had the lost year where Sloan retired midway through. You could argue that year he did a bad coaching job, but most rookie coaches would in that situation. In the last 3 years he did about as good as any coach would have done. His first full season they were a playoff team, his second year they were above .500, and last year they were terrible. Maybe a few great coaches could have greatly exceeded those marks, but only a few select coaches like Pop, Larry Brown, etc... Fans often have higher expectations for their team than what is actually realistic. Corbin never had a team capable of winning a playoff series. His one year of failure was 2012-2013. That team could have made the playoffs, but many years 43-39 is good enough to make the playoffs. That roster was hardly capable of 50+ wins. For all the love Millsap and Jefferson have gotten, their teams were the 7th and 8th seeds last year in the lowly east and of course lost in the first round. Corbin hardly bombed in his 3 years. A great coach could have possibly won a few more games, but those teams easily could have lost a few more too. Nobody expected much from those Jazz teams outside a few homers in Utah.
The truth about the Jazz, is the Jazz do not have great players. There is not one guy on the team outside of maybe Exum that has potential to be a real superstar in this league, and Exum is extremely raw. I don't think Corbin was a great coach by any means, but I don't think Snyder is either. He will go as far as his players will take him similar to every other nba coaches with a few exceptions. I don't care that Corbin was replaced, but I wouldn't care if Snyder was replaced soon either. He should be the coach for a few years, but until the Jazz get better players it won't matter. The rest of the league is not fearful of Hayward and Kanter, sorry.