Criminal are not skilled fighters. You do not need to defeat highly skilled MMA fighters in self defence. Muggers, rapists and other experienced criminals do not dedicate years of their life becoming highly skilled MMA fighters in order to get what they want from their victims.People who've never sparred hard, for full knockouts....and regularly as part of their training, don't really know what a trained & experienced fighter can do in the ring and in the street.
They do not engage in sparring with their victims. You are confusing fighting with self defence, they are two different things.