We may have the same organs in our bodies but they don't function same way, for example our brain, it functions differently there are some set of people there brain captures things easier while some don't, so this is the main reason for knowledge gap, the brain is the reason for it.
When I was in school I have a friend when we always go to library together to read when he reading his Brain grab it at once, but the other friend I have he has to read a particular thing over and over again before his brain can grab it.
There are some set of people when you are explaining something for them there Brain understand what you are talking very fast while some set of people you need to explain it over and over again before they can understand what you are trying to say, if you have a sharp brain you will be smart and intelligent, however you can be smart and intelligent when it comes to education but not when it comes to life, some set of people are not intelligent in teams of school but very intelligent in life.
Education intelligence is different from life intelligence.