It seems that, at the very least, part of the problem has to be the stress of being the linchpin of the commercial pollination industry. The industry is focused on honey production (for the hive owners), and following after the crop cycles of almonds, fruits, and so on.
Bees, for a species that until 130 years ago was content to live in hollow logs to have been domesticated and forced to carry the burden of producing the world's food supply from artificially created homes, some of this is not unexpected.