U decentralize something to protect that something from becoming centralized which would reduce or eliminate that things value.

Ex. If u want the world to know that Satosha is a great person, you would tell as many different people “Satosha is a great person. “

If you only tell one person, I can just find and kill that person and no one would ever know Satosha was a great person.

You diversify when you would rather have something than nothing but you are ok with having less than if you didn’t diversify.

If you were betting on 100M dash and Usain Bolt was in the race against 7 old men , you would put all ur money on Bolt. If it was 8 random old men only you might spread ur money around on 6 of the 8. If one of the 6 wins , at least u get something. If u put it all on runner 1 and he wins you would have gotten more. But then there’s a 7/8 chance u get nothing.