I was involved in the Alaska seafood biz for over 35 years. While over harvest can be blamed for some of problems in catch quota numbers dropping, this reasoning is too simplistic. Both the ADFG as well as NMFS both monitor these crab fisheries ( and all Alaskan fisheries) with an iron fist.
The “heat blob” that overtook the Gulf of Alaska in 2016 had significant effects on both pollock and cod quotas. The fish just disappeared.
The Bering Sea has seen temperature rises in 2019. This effect can’t be discounted.
As far as Chinese Communist fishermen taking our resources, this is simply silly. The Coast Guard is ready and manned to foil any illegal fishing in Alaska. Both king and opilio (snow) crab are caught in relatively shallow shelf waters towards Bristol Bay. They would have to extremely brave or stupid Chinese to fish so close in.