All it says is that they don't yet have strong evidence to expect a conviction on hacking charges. And it's quite likely that some other people were involved in

All it says is that they don't yet have strong evidence to expect a conviction on hacking charges. And it's quite likely that some other people were involved in the hack itself - perhaps after this arrest, they will get some new information that will allow them to charge someone for the hack itself, for example, out of a plea deal when one of the gang turns against the others.