No. 1: Frank Vogel
The Los Angeles Lakers wanted a head coach who had a proven track record of success and knew how to craft an elite defense. They knew they had a window to try and win the title with LeBron James on the team, and they chose Frank Vogel to head up the operation.
The front office also hired former head coach Jason Kidd as Vogel's lead assistant, making it clear from the start that if Vogel couldn't deliver success right away there was a ready-made replacement waiting for the opportunity.
Vogel didn't give Kidd or the front office a chance, leading the Lakers to the title in his first season. They went 52-19 for the year, a 60-win pace, and they had the league's third-best defense. That became the best defense in the playoffs as they smothered opponents once the season restarted in the Orlando Bubble and won the franchise's first title since 2010.
Things fell apart from there, but it's difficult to understand why Vogel was to blame. The following season the team was wracked by injuries, with LeBron James playing just 45 games and Anthony Davis 36. They still made it into the playoffs before losing in six to the Phoenix Suns.
That next offseason LeBron James encouraged the front office to trade away good, proven role players for Russell Westbrook, one of the most disastrous trades in modern NBA history. It destroyed the Lakers' chances of contending for a title, and Vogel unsurprisingly wasn't able to make things work with a roster that was stripped of all the parts that once made it work. The Lakers won just 33 games and Vogel was fired after just three seasons despite winning a title.
Frank Vogel isn't a top-5 coach in the NBA, but if he is given a good roster he can shape it into something great. His defensive coaching in particular is top notch, and he proved in 202 that he can lead the right roster to a title. The Lakers then came down hard on him for not taking a bad roster and making it great, and it's hard to pin that on Vogel. He was a scapegoat for the disappointment the organization experienced and, in some ways, for Rob Pelinka going through with the Russell Westbrook trade.
Without question, Frank Vogel was the best head coach the Lakers have had since the departure of Phil Jackson.