insects just like any other lifeform is sensitive and needs protection. they lay their eggs underground, where they're protected from direct sunlight and the cold winter. if we plough through the dirt every year, it's obvious that we'll disrupt that generational hibernation, and that disrupts the cycle of death and rebirth for the insects, that's why they vanish. I think ploughing is the biggest reason for insects disappearing, though it wasn't listed in the article (or i missed it)
“We could not feed the global human population without [insect] pollinators,”
(that's a quote from the article). I think that's wrong though. Most calories are provided by cereals, and cereals are wind-pollinating, AFAIK.