Many times these things are due to seemingly unrelated events.

I remember the story of why there were no new Aspen trees growing Yellowstone National park.

Everybody was baffled until they finally analyzed the situation and realized that since the last wolf was shot 70 years ago, Elk had no threat. They over populated and and ate all the aspen shoots because they were hanging out in places that would have been dangerous when wolves were still around. They also linked this to water errosion as the Elk were eating all the willow which held the banks of streams at bay when the beavers dammed them.

Could be something similar to that...an indirect ripple effect with unexpected results.