The fake security cameras are a deterrent control. They don’t actually prevent theft and since they aren’t operational cameras they won’t detect if theft is actually happening. They can be a deterrent to thieves who think they are functioning.
Wikipedia
Security controls are safeguards or countermeasures to avoid, detect, counteract, or minimize security risks to physical property, information, computer systems, or other assets. In the field of information security, such controls protect the confidentiality, integrity and availability of information.
Systems of controls can be referred to as frameworks or standards. Frameworks can enable an organization to manage security controls across different types of assets with consistency.