The company i work for deals a lot with the law in china. From...

The company i work for deals a lot with the law in china. From my experience the reason that no charges have been laid as yet is that the Chinese government has no real evidence. They are only holding the Crown staff to try to get a confession.
Companies like Crown would store all their information on a cloud and as soon as the arrests happened the laptops and phones would be nothing more than paper weights. Nothing would be stored on the devices them selfs. All access to crown data for those employees detained would Immediately be blocked.
If, and i stress if they were intentionally breaking the law they probably would have been prepared for this outcome knowing what to expect and how to counter it by leaving no evidence also having the staff prepped. Saying that i don't think they would have broken the law knowing the risk of the long term damage versus short term gain to lift the companies profit.
There was also several public and direct warnings from Chinese authorities that it would not tolerate the recruitment of Chinese nationals to gamble overseas, which had culminated in the arrest of numerous South Korean casino employees. The Crown board knowing this they would have put steps in place to try and avoid the same fate making sure they are acting with in the laws of china.