Because Eliza failed to alert police to Stephanie’s disappearance, and because she chose to adhere to hospital protocol over gut instincts, Bailey fired Eliza, who later packed up her stuff and alerted Arizona to her new occupational fluidity.
Markia Dominczyk’s absence, as reported by TVLine, was also partly predetermined in the Season 13 finale, in the aftermath of the hospital explosion.
It would have been easy to bring her back, at least from this story’s perspective, but I guess it was decided not to be a good idea.