I went to a talk by a lightning expert a few months ago. He said it's thought that essentially all lightning is triggered by cosmic rays. The lightning would eventually go off spontaneously, but there are enough cosmic rays that it never gets that far.

Also, some of the electrons in the lower radiation belt are launched into orbit by lightning, in effect as recoil. And there is a steady drizzle of electrons that get decelerated by collisions and fall back into the atmosphere. So there is an electron current between earth and space, driven by lightning.

Well, as someone who grew up in the Midwest and saw lots of spectacular lightning, it's not surprising that it has spectacular effects.