It's static electricity. To be simple and short just as you wipe electrons free from the rug when you walk and they collect on your shoe and conduct everywhere from your fingertips to your head, the wind does the same. The charge collects in the atmosphere. WInds are greater in storms and the water droplets act as dielectrics collecting and concentrating charges.
When charges are separated, an electric field results. The more charge, or the smaller the distance of separation, the higher the field. Air and moist air can only support a certain field before the air breaks down into a plasma(separate charges) and conducts. The conduction is the lighning bolt. The measure of electric field strength is in volts/unit length.
And you don't think God directs lighting strikes?
That was my point. Do you think that it is a random occuranance whether the victim is a child molester or a Boy Scout?