I may just be interpretting this discussion different than everyone else here, but assuming every developer is happy with company, and company decides to implement a new development philosophy or production model (for strategic / financial / etc..) reasons, wouldn't it be sensible and actually expected that a non-trivial number of developers won't be happy with said changes?
For example, If my company went from Dev and IT groups to merging them into devops, some people are going to be rocking the idea, and a shit ton may be unhappy about the change and decide to move on. DevOps isn't any more or any less better for an employee, but it means a different set of tasks for that developer to live in. Maybe this change will significantly improve workplace productivity and the change isn't only merited, but essential for the company's survival. Same with, say dropping support for Windows/Linux/Mac/etcc OS's and just supporting a smaller set of OS's. Some would say there are valid reasons to adopt the standard (less IT burdens), and others who use said dropped OS's will be more willing to leave.
To assume that the company simply doesn't care about its developers walking out is a little bit of an overstatement. Many won't like a change (regardless of what it is), and if you're going to leave, you might as well leave when you perceive a negative change in your job.