Despite the fact that it's Boston, it's a drastically unappealing job. The Red Sox seem to constantly have a roster full of whiny, entitled babies. Farrell was actually a perfect manager for them, since he's a whiny baby himself.
The fact they ran Francona out of town proves that it's a brutal place to manage, even if you're one of the best. I wouldn't be surprised if Cora was the only person interested in the job.