The definition of a kingdom is "the territory or country subject to a king; an undivided territory under the dominion of a king or monarch." In other words, its king determines the qualities, characteristics, and nature of a kingdom. Those that dwell in that territory must have an understanding that it is the king that determines their way of thinking and living.
We don't understand these qualities or characteristics that make up a kingdom. And because we don't fully understand it's difficult to get the full revelation of the kingdom of God.
Jesus says that it is our heavenly Father's good pleasure to give us the kingdom. But to receive the kingdom we must recognize and understand the king so we can receive the kingdom.