No one here is going to take the time to explain this.

Short story:

Aircraft engines often have two ignitions systems for safety. To understand why they went to the trouble of putting two plugs (but essentially not two separate systems) in our engines, type this into a search engine:
why do some automotive engines have two plugs per cylinder it is an interesting read.

If you don't think two plugs per cylinder are needed, remove the second plug wire from each coil pack and see what you get.