There was simply no comparison between Malik Zaire and Deshone Kizer.
Kizer was easily the better quarterback, and could make all of the throws. Zaire was put in more of a nurturing position, where he was simply asked to not make mistakes.
The fact that he had some pretty good numbers in 2016, despite not having a true #1 WR (St. Brown did step up his game towards the end), shows that he was the man for the job.