The purpose of bullying is to hide inadequacy.
Good managers manage, bad managers bully.
Bullies bully to hide their weakness and inadequacy, and to divert attention away from their incompetence.
Many employers don't want to calculate the cost of low morale, poor productivity, poor customer service, high sickness absence, high staff turnover and frequent grievance and legal action that are a consequence of "tough dynamic management".etc.
Bullying results in demotivation, demoralisation, disenchantment, disaffection, disloyalty, ill-health, high sickness absence, high staff turnover, an us-and-them culture, low productivity, frequent mistakes, low morale, non-existent team spirit, poor customer service, no continuity of customer care, etc.
And that's just for starters.
a) Just tough management
b) Persistent unwelcome behaviour
c) An effective way to increase productivity, profit and performance in an organisation