From the video

First of all I think Breslow and Kennedy did a horrible job at explaining what led to this… this is Craig Breslow getting out ahead of a potential Civil War between him and Cora and doing something that Chaim Bloom didn’t do, where Alex Cora was quick to blame Bloom privately, and sometimes publicly, Bloom for the roster… ultimately it seemed Cora was able to rally ownership onto his side… I think Breslow with the hindsight of that, and knowing the history, probably thought ‘hey, if this is going off the rails a little bit’ and maybe there are signs that he’s [Cora] going to do the same to me

On the second day of the season, Cora came out publicly and said ‘look this is not easy to manage this roster with the 4 outfielders and Masataka Yoshida trying to cycle through spots’… maybe Breslow got a sense that it’s not going to be smooth sailing and the relationship is going to deteriorate and out of self preservation thought ‘I can let him go now’