Jo Wilson proved long ago that she was a fighter on Grey's Anatomy. Living through domestic abuse at the hands of her first husband and learning that she was the product of rape directly from her birth mother are just two of the many obstacles this character has had to overcome. It's also why Jo was able to get over Alex's Grey's departure so quickly. Because showrunner Krista Vernoff just couldn't bare to see Jo go down another dark path after already going through so much earlier in the season.
“I didn’t want to put anyone through it,” Vernoff explained to TVLine during a recent interview. “[Camilla Luddington] had so beautifully gone through many months of very dark storytelling, and I didn’t want any of us to watch Jo go into a hole again.” Jo had succumbed to a mental breakdown earlier the season after the discovering the truth about her birth parents. The pain of it all became too much to handle, prompting Jo to seek treatment for the sake of her mental health. It was a long road to recovery, but considering how far Jo has come, it makes sense that the writers were more than willing to give her a break.
However, that wasn't the only reason Vernoff felt Jo should make such a fast rebound after Alex's betrayal. Because while it may have been tough to learn via a Dear John letter that her husband had run off to be a family with his ex-wife Izzie Stevens and their twins, the EP believed her reaction to it all "felt honest" and gave Jo the tools she needed to be able to move on.
"I’ve had the experience in my life where the pain of not knowing is so much worse than a very painful truth," Vernoff revealed. "Jo had so many episodes of not knowing [where Alex was] that even though the answer was horridly painful, there was really honest relief [in just knowing the truth]. Getting an answer finally allowed her to strangely feel better than she had when she was just in the dark."
Prior to receiving Alex's letter, Jo had begun envisioning every possible worst case scenario. Was Alex injured or dead in a ditch somewhere? Was he having an affair? Did he just want to be away from her? Jo had been completely left in the dark. "It felt like she had done a lot of grieving for the relationship in the weeks prior to receiving that letter," Vernoff added. So really, there was no need to drag it out any longer.