While many fans were thrilled to learn of producers' surprising choice, supporters of Peter -- the apparent fan favorite and frontrunner for the role -- were devastated.
"Peter was absolutely in discussion. He sort of alluded to that as well. I think at this point in his life, the breakup with [Rachel Lindsay] was still very raw," ABC reality programming executive Robert Mills toldEntertainment Tonight.
"Sometimes you move on very quickly, sometimes you don't. I think that, for him, there were still residual feelings there, and it was a very real breakup. They all are, but this was tough."
Peter seemed totally in love with Rachel on The Bachelorette's thirteenth season, but when it became time to propose marriage, he realized he wasn't ready for that type of commitment. Rachel, on the other hand, refused to leave the process with just a boyfriend, and not a fiance.
Peter and Rachel therefore had an excruciating and emotional breakup before the final Rose Ceremony in which Rachel ultimately chose Miami-based chiropractor Bryan Abasolo. Peter, at the time of filming, wanted to continue dating Rachel in the real world more than anything, but the pair couldn't agree on the post-show terms of their relationship.
"I think the finale, when that aired and everything after that was also hard on Peter. I think he just didn't know. I think Peter probably would have done it and been an amazing Bachelor, but I also don't know if he, himself, knew if this was the time when he was ready to really do this 100 percent," Robert explained.
"I think we'll always be in touch with Peter, and there might be a time... It might be a year from now, when it's better for him. It was all about timing. If Arie wasn't ready, we would have looked at him, but we want it to feel right."
So did Peter's refusal to pop the question to Rachel really play a role in producers' decision to cast Arie as the next Bachelor instead?
"I think it was just both sides saying, 'You know what? It's not 100 percent right. Let's wait and do this when it's 100 percent right.' We develop real feelings and relationships for these guys. It's hard," Robert said.
"I personally love him, and I hope The Bachelor or another Bachelor option, something, we do something with Peter down the road, because he's a great guy. And that came through on his season of The Bachelorette, why so many people like him."
In addition to losing the woman he was crazy about, Peter also had to deal with media scrutiny and even death threats from fans during and after his The Bachelorette experience.
Part of Peter's hesitation to take on the role of The Bachelor star therefore probably stemmed from fear of more backlash, especially if he ended up being reluctant to propose again to the bachelorette of his choice at the end of the season.
"Peter was an incredible fan favorite, which I think was great, but I also think the double-edged sword with that is, if it's not the season that the fans want, which, you know, might have been if Peter might not have been ready to commit 100 percent, that's also disappointing, and it would have been disappointing for Peter too," Robert told ET.
Casting talks and negotiations with Peter, however, "absolutely" ended on good terms, according to the ABC executive, which is consistent with Peter writing on Instagram yesterday that he's grateful and humble the network had treated him with "love and kindess."
Maybe Peter's fans will see him on The Bachelor Winter Games or Bachelor in Paradise next year, or a future edition of The Bachelor.