BTC is a high risk speculative asset. A BTC investor should know it.
You cant just say it like that. Investors carry on certain risk, ofc, but there definetly needs to be some regulation to stop thing like this from happening.
It is not the first case of bitcoin missuse, and scamming through bitcoin, and that is one of reasons bitcoin doesnt have more investors.
Some say regulation will ruin bitcoin due to centralisation of some kind, but actualy heavy regulations are needed to give bitcoin a chance to move forward.
These "investors" were not informed about the lack of regulations? I guess they were well informed and were gambling with the unregulated, highly speculative and risky asset. If you are investor, not "amateur" - you should take all risks, including the possibility of criminal issues.