As stressful as selling a home and moving to another is for people . . . it can be even more so for animals.
Specifically, the family pet(s).
The obvious reason: there’s no way to explain to them what’s happening (at least that I know).
Extra attention, exercise, and TLC ” and if that doesn’t work, a (temporary) course of canine Valium (a real thing ” and a life saver for at least one dog-owning client of mine).