To put it succinctly, people come in varying degrees of intellect from the average to highly prodigious. Some average people contend that they are the smartest thing on two legs while there are highly prodigious people who are quite humble, believing that they can learn from anyone. Conversely, there are those of prodigious intellect who believe that they are the intellectual elite or untermenschen while other people, in their opinion, are slow, retarded, stupid, and are not of high intellectual calibre. There are those of average intellect who know that they are smart but so are others.
Being intelligent is knowing how to successfully access and navigate life and situations. There are many highly intelligent people who do not possess basic life and survival skills. Although they are highly educated and intelligent, they struggle throughout life because they do not have the prerequisite people, life, and survival skills whereas there are average people in terms of educational attainment and intellect who are highly successful because they have sublime personal, life, and/or survival skills.