Police involvement in these sorts of things is a lot more complex than people realise. Police are an enormous resource on the tax payers. They are a required tax expense but a single officer costs a lot. Paying them to guard a hotel when you can sub it out to another company for a fraction of the cost is just logical. Putting police officers there also means that they're diverted from their other duties. You're not going to hire officers just for this one task.
It's a real issue in the security industry. They recently released new rules on police responding to alarms that requires that police only be dispatched by an A Grade rated monitoring centre, and only dispatched with actual confirmation of a crime in progress. And any security company that accidentally breaks those rules multiple times (like sending police to false alarms) gets black listed meaning that police will consider any alarms from that company to be low priority. A black listed monitoring centre basically get screwed.
All these new rules come in because police resources are drawn thin and response times from police are getting longer and longer putting lives at risk.
Our Govts, of all persuasions, entrust and outsource the country's security needs for all kinds of tasks eg jails, Manus Island, 150 (apparently?) guarding the Sri Lankan family of 4 on Christmas Is., Centelink and Medicare Offices, airports, defence bases, both land and ports. There was no real dereliction of duty on behalf of the Victorian Govt when the use of private security is common practice these days.
The real problem seems to be the sub contracting then further sub contracting involving 3 companies, which the original security firm let out with no supervision, training or accountability.