The current CEO and CFO uncovered this mess. The two Chinese...

The current CEO and CFO uncovered this mess. The two Chinese directors quickly departed, there's missing cash and paperwork related to cost of sales that just doesn't add up. KPMG clearly DO agree that something as badly amiss because they can't ascertain the beneficiary of payments and that there is a connection with the chinese directors. So I'm not sure how you came to your conclusion that KPMG don't agree that fraud has taken place.
The company clearly wasn't properly set up to run a Chinese based business with accounts in Chinese and payments managed by Chinese. Directors responsible for that? Ultimately yes IMO.
This lack of governance allowed the alleged fraud to take place.
Class action? Dunno. Like others, I can't see the logic of wrecking your own company. But I do have a strong view that the company should use every available means to go after the perpetrators, for a while. I don't want the distraction of chasing people for some cash to derail the opportunities ahead to rebuild this business.