Fear + Silence = Angry Employees.
You’ve hammered out the details, gotten board approval and told the employees about the Big Change (i.e. merger, new software, department consolidation, etc.).
It’s a good deal for all involved. So, why are the employees so angry?
Because Big Change creates fear. Unless there is clear and consistent information explaining, “What Big Change means to me,” they will resist the new way of doing things.