The original article mentions few reasons what may be going on in Germany—industrial scale use of pesticides or the increase in farms dedicated to a single crop. The same factors plus better crops and fertilizers allowed for 10x increase in crop productivity (check this truly amazing graph https://www.agry.purdue.edu/ext/corn/news/timeless/images/CornYieldTrend_US.gif)
Industrial farming is progressively more decoupled from ecosystems and does not need rich ecosystems (imagine hydroponic indoor farms growing vegetables just from water, artificial nutrients, and under LED light)
Also my guess would be you are overestimating importance of insects (copared eg to bacteria)
Some speculation
The original article mentions few reasons what may be going on in Germany—industrial scale use of pesticides or the increase in farms dedicated to a single crop. The same factors plus better crops and fertilizers allowed for 10x increase in crop productivity (check this truly amazing graph https://www.agry.purdue.edu/ext/corn/news/timeless/images/CornYieldTrend_US.gif)
Industrial farming is progressively more decoupled from ecosystems and does not need rich ecosystems (imagine hydroponic indoor farms growing vegetables just from water, artificial nutrients, and under LED light)
Also my guess would be you are overestimating importance of insects (copared eg to bacteria)