Groucho Marx made a career of skewering the pompous.  One of his favorite targets was the stereotypical college professor.  The professor was always exceedingly dignified, confident of his knowledge--and sure that his students would never get it.
Jesus has something like that in mind here when he speaks of the "wise and learned."  These are those who base their evaluation of others upon their scholarly learning, looking down on the ignorant.  It is their faith that no one without a doctorate in their particular field could possibly understand anything about it.
Our Lord then tells us that God has turned this on its head.  Instead of making his truth known only through years of hard study, he makes it so simple that even little children--the word is also used of "babies" - can understand it.  The phrase is very encouraging:

• It is encouraging because we all started out as little children.  He removes the fear that we'll never get to the right level of understanding.
  
• It is encouraging because children are the fastest learners, and we shall understand what God wants, quickly.
  
• It is encouraging because little children are humble (or were in Jesus' time), and so our knowledge of God does not depend upon our position in life, or in the church.
  

• First, so that the door to Him might be opened wide--and thus no one would be unable to come to him.
  
• It was revealed--not discovered--so that no one would boast about it.  Each of us gets it as a gift.