The expression "Lightning never strikes twice (in the same place)" is similar to "Opportunity never knocks twice" in the vein of a "once in a lifetime" opportunity, "i.e.", something that is generally considered improbable. Lightning occurs frequently and more so in specific areas. Since various factors alter the probability of strikes at any given location, repeat lightning strikes have a very low probability (but are not impossible). Similarly, "A bolt from the blue" refers to something totally unexpected, and "A person being struck by lightning" is an imaginative or comedic metaphor for someone to experience a once in a lifetime, striking, sudden lightning-speed revelation, similar to an epiphany or an enlightenment.