From my perspective of many decades of experience and some trips to CA before I went all stationary, what's not spoken about is mite treatments, hive inputs and success in CA.
From the 2 dozen of so beeks I know in Wi/MN that go to CA it seems like a pattern of the beeks that have kept their brood comb clean and free of apistan/checkmite and off label miticides have good success in CA and the following summer.
Its typically the same bunch of beeks that complain about heavy losses also have a long history of off label mite treatments. Many fo these guys have enforcement actions from Sodak and MN and have used a myriad of treatments some of which I don't want to mention for fear of someone else trying them.
Comes down to some very experienced beekeepers lost their magic when they started tossing homemade mite treatments (and 2 or more antibiotics/yr, pollen subs, essential oils, syrup etc) into hives multiple times a year and now have contaminated brood comb and a host of problems.
Sure they have lots of experience to draw from etc but playing chemistry set with their bees year after year is not something they have the education or skill to comprehend what the affects mite bee.
Even the top bee researchers will tell you that the synergy between multiple chemical treatments in hives is not something that is well understood. And I'm not sure its something we need to have research conducted on either since some of these are illegal treatments .
I see some newbies and pro's still think that micrograms of trace pesticides brought into hives somehow trumps the massive levels of chemicals and additives that some beekeepers INTENTIONALLY put into their hives multiple times a year.
Getting back to the basics and designing a bee business around the concept I SHALL PUT MINIMAL INPUTS IN MY HIVES AND STRIVE FOR NONE is in my view the key for successful commercial beekeeping for the next decade.
The Last Beekeeper could be more accurately titled: The Last Industrial Beekeeper. Think about it....