As a bee owner myself (as a hobby), the reality is usually 33% of hives don’t make it Through the winter. This was known back in the 70’s and probably much further (I have a book from then which covers the subject of bee keeping).
From the linked article - 40% seems a tad higher, but if you don’t over winter the bees, have a tough year, w.e. You run a risk.
IMO one of the big issues is lack of biodiversity. Bees need pollen and if they collect pollen from almond fields only, they might not have enough stores because they only bloom for a specific time of year. Further, bees need ready access to water, which deserts / bees on the road dont provide.
Finally, yes pesticides are likely a problem, but again that’s because we are bringing bees to a farm which sprays the stuff.
https://www.sciencemag.org/news/2019/07/breeders-toughen-bee...
https://www.genengnews.com/news/honey-bee-microbiome-bacteri...
https://beecare.bayer.com/media-center/news/detail/a-new-way...
https://minnesota.cbslocal.com/2019/05/30/program-to-help-mi...
https://www.independent.co.uk/environment/nature/victory-for...