Hollins' dismissal was reasonable, because he had been stubborn and incompetent in last season's playoffs.
Being stubborn is relatively minor; many famous coaches have this trait since their renown suggests they've had past successes. Their stubbornness often stems from an inability to adapt to the evolution and changes of basketball.
Incompetence, however, is fatal. Whether facing Popovich or Carlisle, he was utterly outclassed.
When a team sets its sights on contending for a championship, his firing was nearly inevitable.
After all, in the NBA, a head coach is much cheaper relative to players.
What surprised Hansen was the timing of this decision.
If the management had realized the issues with Hollins after the playoffs, they should have fired him then, which would have given them time to choose a new coach.
If the management wanted to further evaluate Hollins, they should have made a decision after some time had passed since the season started.